Can I file an FBAR without bank statements?

Yes. The maximum value of an account is a reasonable approximation of the greatest value held during the calendar year, and Publication 5569 permits reliance on periodic statements issued at least quarterly where they fairly reflect the maximum. Where statements are unobtainable, reconstruct the figure from interest certificates, HMRC records or mortgage files, document the source and the inference, and report a conservative figure rather than leaving it blank.

How do I get old bank statements from a UK account I closed years ago?

Send a written subject access request to the institution's data protection officer, naming all former names, addresses and account numbers, and the specific calendar years you need. GOV.UK confirms the organisation must supply the data within one month at most, and that such requests are usually free. If the institution has merged or rebranded, trace the successor through Companies House and the FCA register and name the predecessor entity in your request.

How long does a UK bank have to respond to a subject access request?

One calendar month, extendable by up to two further months for a complex request if the bank notifies you within the first month. ICO guidance treats technical difficulty in retrieving electronically archived information as a valid ground for that extension, which is common for six-year-old records. If the request is ignored or refused, complain to the ICO within three months of the last meaningful contact with the organisation.

Do UK ISAs, SIPPs and Premium Bonds go on the FBAR?

Cash ISAs, stocks and shares ISAs, SIPPs, personal pensions, NS&I products including Premium Bonds, platform and nominee accounts, and e-money accounts are all foreign financial accounts for FBAR purposes, whatever their UK tax treatment. Reporting is per account once the aggregate of all foreign accounts exceeds $10,000 at any time in the year, so small and dormant accounts must be listed too.

Can I amend an FBAR later once the missing statements arrive?

Yes, and the IRS expressly directs filers without complete information to file as complete a report as possible by the October 15 automatically extended due date and amend the report later. To amend, mark the Amendment Indicator, enter a new Date of Signature and complete all other applicable fields in their entirety. A FinCEN amendment is a full re-filing rather than a partial correction, so retain your workpapers in rebuildable form.

Missed FBAR: Rebuilding Six Years of UK Records

Q: Do I use the highest balance or the year-end balance on the FBAR?

The highest value reached at any point during the calendar year, not the year-end balance. IRM 4.26.16.2.2.2 describes it as the largest amount of currency and non-monetary assets appearing on any quarterly or more frequent account statement for that year. The year-end date matters only for currency conversion: you translate the sterling peak at the Treasury Reporting Rate of Exchange for the last day of that calendar year.

A missed FBAR is corrected by electronically filing the late FinCEN Form 114 through the BSA E-Filing System, selecting a reason for late filing, and reporting a reasonable approximation of each account's maximum value. You do not need a complete set of statements to file. IRS Publication 5569 states the rule plainly: when a US person learns they should have filed an FBAR for an earlier year, they should electronically file the late FBAR using the BSA E-Filing System, entering the calendar year reported, including past years, on the online FinCEN Form 114.

That single sentence dissolves the most common reason UK-resident Americans stay non-compliant for another year. They believe the filing is blocked until every statement for every account is in hand. It is not. The maximum value of an account is, in the words of Publication 5569, a reasonable approximation of the greatest value of currency and non-monetary assets in the account during the calendar year. Approximation is the standard the regulator wrote, not a concession you are asking for.

What follows is the working method we use to rebuild six years of UK banking, investment and pension records for a catch-up filing: how to extract data from a UK institution under UK data protection law, what to do when the institution has merged or disappeared, which derivative UK documents reconstruct a peak balance when statements are gone, how to convert sterling correctly across six separate year-ends, and which of FinCEN's late filing reason codes actually fits a documentation-driven delay.

What is the current route for filing a missed FBAR?

There are two live routes, and it matters that you name them correctly. The first is filing the late FinCEN Form 114 directly through the BSA E-Filing System and selecting a reason for late filing. The second is the Streamlined Filing Compliance Procedures, which for US persons living in the UK usually means the Streamlined Foreign Offshore Procedures. Details of both are on irs.gov, at https://www.irs.gov/individuals/international-taxpayers/streamlined-filing-compliance-procedures and https://www.irs.gov/individuals/international-taxpayers/u-s-taxpayers-residing-outside-the-united-states.

A third route that many articles still describe no longer exists as a named, separately published IRS procedure. The IRS withdrew its standalone webpage describing a delinquent FBAR submission procedure around 30 June and 1 July 2026. If a page you are reading tells you to follow that named procedure and links to a page that no longer resolves, the page is stale, and stale guidance on a penalty-bearing filing is a real risk. What survives is the substance rather than the brand name: you file the late FBAR, you give a reason, and Publication 5569 confirms that if you properly report the foreign financial account on a late-filed FBAR and the IRS determines the violation was due to reasonable cause, no penalty will be imposed.

The practical difference between the two routes is scope. Filing late FBARs directly addresses the FBAR only. The Streamlined Foreign Offshore Procedures address the income tax returns and the FBARs together, and a taxpayer who properly completes the programme will not be subject to failure-to-file and failure-to-pay penalties, accuracy-related penalties, information return penalties, or FBAR penalties. If the underlying US returns were also missed or understated, the reconstruction work described below feeds a streamlined package rather than a standalone FBAR filing. Our overview of that programme sits at us-uktax.com/streamlined-foreign-offshore-procedures.

How many years of late FBARs should you file?

Six. The Streamlined Foreign Offshore Procedures require delinquent or amended tax returns for the most recent three years for which the return due date has passed, and any delinquent FBARs for the most recent six years for which the FBAR due date has passed. Six years is also the shape of the civil enforcement window: IRM 4.26.17.3.1.1 applies the six-year period beginning on the date of the transaction under 31 USC 5321(b)(1), and for a failure-to-file violation that date is the FBAR due date for the year in question.

That has a sequencing consequence almost nobody articulates. The six-year assessment clock runs separately for each year, from that year's own due date. While you are waiting three months for a UK bank to answer a records request, the oldest year in your six-year window is aging. This is not a reason to delay a filing in the hope a year falls away, which is a strategy that fails badly if the facts are ever examined. It is a reason to sequence the work: open the record requests for the oldest years first, because they are simultaneously the hardest to evidence and the ones with the least time left in flight.

Note also what triggers the obligation. A US person must file an FBAR if the aggregate value of their foreign financial accounts exceeded $10,000 at any time during the calendar year reported, per https://www.irs.gov/businesses/small-businesses-self-employed/report-of-foreign-bank-and-financial-accounts-fbar. Aggregate is the operative word. Publication 5569's own worked example has a filer with accounts of $100, $12,000 and $3,000, and requires all three to be reported, because the aggregate of $15,100 breaches the threshold. A dormant current account you had forgotten is reportable once the aggregate is crossed.

Why is the sixth year the hardest to evidence?

Because the retention rules on both sides of the Atlantic fall short of it. Under 31 CFR 1010.420 you must retain FBAR records for five years from the due date of the report, which is 15 April of the year following the calendar year being reported. Your own legal retention duty therefore never covered the sixth year back. On the UK side, the Money Laundering Regulations require regulated businesses, including banks, to keep customer due diligence and transaction records for five years beginning from the date a business relationship ends or the date a transaction is completed, as set out at https://www.gov.uk/guidance/money-laundering-regulations-your-responsibilities. That is a floor rather than a ceiling, and many institutions keep more for longer, but it means year six sits outside the minimum on both sides at once.

The same regulations explain why retrieval can be slow even when the data does exist. UK anti-money-laundering records may be held as originals, photocopies, microfiche, scanned, computerised or electronic. A six-year-old closed-account file may be sitting in an archived format that no branch or call centre can reach, which is a genuine operational fact rather than an excuse, and it becomes relevant later when a bank invokes an extension to your data request.

Which UK accounts belong on the FBAR before you start reconstructing?

Reconstruction fails at step one if the inventory is wrong. Build the account list before you chase a single statement. For a high-net-worth UK-resident filer, the population is usually far wider than the current account they first think of.

Current accounts and savings accounts, including accounts closed part-way through a year
Cash ISAs and stocks and shares ISAs, which are ordinary foreign financial accounts for FBAR purposes despite their UK tax treatment
SIPPs and other UK personal pension arrangements, and employer scheme accounts where you hold an account interest
NS&I products and Premium Bonds
Offshore bonds and single-premium investment contracts
Investment platform, nominee and wrap accounts, including accounts holding only funds
Spread betting and CFD trading accounts
E-money and neobank accounts, which are frequently forgotten because they live only in an app
Employer share scheme accounts holding shares or cash on your behalf
Accounts over which you hold only signature authority, including business accounts of a UK company you direct

Crown Dependency accounts deserve a separate line. A Jersey, Guernsey or Isle of Man arm of a familiar UK brand is a distinct legal entity in a distinct jurisdiction, and UK data protection law does not apply there in the same form. That changes the retrieval strategy entirely, because the leverage described in the next section is UK leverage. For those accounts you are relying on the institution's own client records policy and on relationship contact rather than on a statutory clock.

How do you get old statements from a UK bank you have left?

Use a written subject access request under UK data protection law, addressed to the institution's data protection officer rather than to general customer service. GOV.UK sets out the mechanics at https://www.gov.uk/data-protection/find-out-what-data-an-organisation-has-about-you: the organisation must give you a copy of the data they hold about you as soon as possible, and within one month at most. Requests for information are usually free, although organisations can charge an administrative cost in some circumstances. That last point is worth knowing before a bank quotes you a per-statement fee for what is properly a data request.

The clock is a calendar month, not thirty days, and the ICO's position is that a firm cannot add days for a short month: a request received on 31 January must be answered by 28 February. Where the due date falls on a weekend or a public holiday, the organisation has until the next working day. A bank can extend by up to two further months for a complex request, provided it tells you within the first month, and ICO guidance expressly treats technical difficulty in retrieving electronically archived information as a ground for that extension. For six-year-old records that extension is likely to be invoked legitimately, so build a three-month worst case into your filing timetable rather than discovering it in September.

Make the request precise. A vague request produces a vague response and restarts the clock in practice, if not in law.

State your full name, all former names, date of birth and last known address held by the institution
Give the account numbers and sort codes if you have them, and the approximate opening and closing dates if you do not
Ask specifically for statements or transaction data for named calendar years, and for the highest balance recorded in each of those years
Ask separately for the five data points FBAR recordkeeping requires: the name in which the account is maintained, the number or other designation identifying it, the name and address of the institution, the type of account, and the maximum value during each period
Ask for annual interest certificates and tax deduction certificates for each year, which are often archived separately from statements and are far easier for the institution to produce
Date the letter, keep proof of sending, and diarise the one-month deadline

If the institution ignores you, refuses without explanation, or supplies an obviously incomplete response, escalate to the Information Commissioner's Office. The ICO's guidance is that a complaint about a mishandled or refused subject access request should be raised within three months of the last meaningful contact with the organisation, so do not let a dormant complaint drift. The escalation is worth making even when it will not produce the data in time, because the paper trail itself has evidential value in your filing.

What if the UK institution has merged, rebranded or been dissolved?

UK retail finance has been through building society conversions, bank mergers, brand retirements and platform consolidations, and the entity named on a decade-old statement is frequently not the entity that now holds the file. The task is to identify the successor and address the request to it. Work from the company number on the old correspondence through Companies House to trace the corporate history and any change of name or transfer of engagements. Cross-check the current authorised entity on the Financial Conduct Authority register, since a rebranded consumer name usually still maps to an authorised firm. Then ask the successor's data protection officer specifically for records inherited from the predecessor entity, naming that predecessor, because a search run only against the current brand will miss them.

Where an institution has been dissolved rather than absorbed, there is no successor data controller to compel. Accept that early rather than burning two months on it, record the fact in your file with the evidence of dissolution, and move directly to derivative evidence. A documented dead end is itself part of the reasonable cause record, and it is considerably stronger than an unexplained gap.

What if you cannot remember which institution held the account?

This is common for accounts opened before a move to or from the UK and then left untouched. GOV.UK's publication on the dormant accounts scheme, at https://www.gov.uk/government/publications/the-dormant-accounts-scheme, explains that an account is treated as dormant where it has been untouched for a minimum of 15 years and the bank or building society has been unable to trace the owner. Ownership is not lost: owners are able to reclaim the cash amount at any time, and should in the first instance contact the business that held their money.

Where you cannot identify that business, the UK government recognises mylostaccount.org.uk, launched on 30 January 2008, as a free cross-industry service supporting owners to find their dormant accounts. It is the correct first step for a US person facing an FBAR reconstruction who genuinely cannot recall which UK institution held a long-closed account, and it costs nothing. It appears in no competing FBAR article we have reviewed, which says more about those articles than about the service.

What derivative UK evidence rebuilds a peak balance?

When statements are genuinely unobtainable, you reconstruct the maximum value from documents that captured a dated balance for another purpose. This is the part of the work that separates a defensible reconstruction from a guess, and most of the sources are documents a UK-resident client already holds or can obtain within days.

Annual bank interest certificates and tax deduction certificates, which fix the interest credited and allow a balance to be inferred from the product's rate for the year
HMRC self-assessment records and SA302 tax calculations showing declared savings and investment income
P60s and employer documents evidencing gross interest and share scheme holdings
ISA annual statements and platform valuation reports, which usually survive longer than transactional statements
Mortgage and remortgage affordability files, which capture a dated snapshot of savings and investment balances at application
Solicitor completion statements from a property purchase or sale, showing funds held and transferred on a specific date
Credit reference agency files, which evidence the existence, opening date and closure date of accounts even when balances are absent
Your own contemporaneous records: emails confirming transfers, screenshots, old spreadsheets and app exports

A property completion or a mortgage application is often the single most valuable document in the file, because it forces a dated, third-party-recorded declaration of liquid balances at exactly the kind of moment when balances peak. If a client sold a UK property in a given year, the completion statement frequently pins the highest balance of that year to the day.

What do you report if you do not know the maximum account value?

You report a reasonable approximation, and you document how you reached it. FinCEN and the IRS have set the standard low enough to be workable and high enough to require method. Publication 5569 confirms that US persons may rely on periodic account statements issued at least quarterly to determine the maximum value of the account if the statements fairly reflect the maximum account value during the calendar year. IRM 4.26.16.2.2.2, at https://www.irs.gov/irm/part4/irm_04-026-016, puts the same idea more mechanically: the maximum value is the largest amount of currency and non-monetary assets that appear on any quarterly or more frequent account statement issued for the applicable year.

Note what that does not say. It does not say the true intra-quarter peak. If four quarterly statements are all you can obtain, the highest of those four is an accepted basis. It follows that partial data is often sufficient data. Note also that you report the highest value reached during the year, not the year-end balance, which is one of the most frequent errors in a self-prepared catch-up filing.

Keep the language of reasonable approximation and avoid the language of estimate. They mean much the same thing in ordinary speech, but only one of them is the regulator's own word, and a file that says estimated invites a completeness challenge that a file saying reasonable approximation, supported by the following sources, does not. Build a one-page maximum-balance workpaper for each account for each year.

The account identifiers and institution, matching the five recordkeeping data points under 31 CFR 1010.420
The primary source relied on, described exactly: a quarterly statement dated X, an interest certificate for tax year Y, a mortgage application dated Z
The inference applied, stated in one sentence, for example interest credited at the product's advertised rate implies an average balance of approximately the stated figure
The conclusion in sterling, and a note of any deliberate conservative overstatement applied
The record of what was requested from the institution, when it was requested, and what came back

Deliberate conservative overstatement is the right instinct here. FBAR liability is not driven by the reported value; the form reports, it does not assess. An overstated but documented figure carries no tax cost and demonstrably cannot understate the account. A blank, or a figure with no stated basis, is the version that looks like concealment years later.

Should you tick the Item 15a amount unknown box?

Usually not, and this is where most published guidance goes half-right. Item 15a on FinCEN Form 114 is the amount unknown box, and the instruction is to check this box if the value of the account cannot be determined. Pages that mention it present it as a general fallback for any account you cannot value. FinCEN's own framing is narrower. The instruction addresses United States persons with a financial interest in or signature authority over fewer than 25 accounts that are unable to determine if the aggregate maximum account values of the accounts exceeded $10,000 at any time during the calendar year, and tells them to complete the appropriate Part II, III, IV or V section for each of these accounts and check the amount unknown box, item 15a.

Read that carefully and the box is about being unable to determine whether the aggregate crossed the threshold at all. If you know perfectly well that a SIPP held a six-figure sum and you simply lack the exact peak, you are not in that position, and ticking 15a across six years of a streamlined package reads as an unwillingness to engage rather than an inability to determine. Use the reasonable approximation the regulator authorises, and reserve 15a for the genuinely undeterminable account, documented as such.

What exchange rate converts GBP to USD on the FBAR?

Use the Treasury Reporting Rates of Exchange for the last day of the calendar year being reported. Publication 5569 adds the fallback: if no Treasury Financial Management Service rate is available, use another verifiable exchange rate and give the source of that rate. Six years of sterling accounts therefore require six separate conversions at six separate year-end rates. You do not convert at the date the peak occurred, and you do not use an average. Reported maximum values are then rounded up to the next whole dollar, and FinCEN's own worked example is that the amount $15,265.25 would be recorded as $15,266.

A six-year sterling worked illustration

The following figures are an illustration only. The sterling balances are invented and the exchange rates are assumed rates used purely to demonstrate the method; they are not published Treasury Reporting Rates of Exchange, and the actual published rate for each year-end must be used in a real filing. The filer is a UK-resident US citizen with a current account, a stocks and shares ISA, and a SIPP opened partway through the period. Year 1 is the oldest year in the six-year window.

Year 1, assumed rate 1.22: current account peak GBP 4,200 equals $5,124; ISA peak GBP 2,900 equals $3,538; aggregate $8,662. Below $10,000, so no FBAR is required for Year 1.
Year 2, assumed rate 1.38: current account peak GBP 4,300 equals $5,934; ISA peak GBP 3,050 equals $4,209; aggregate $10,143. An FBAR is required.
Year 3, assumed rate 1.25: current account GBP 5,100 equals $6,375; ISA GBP 6,400 equals $8,000; SIPP GBP 18,000 equals $22,500; aggregate $36,875.
Year 4, assumed rate 1.31: current account GBP 6,900 equals $9,039; ISA GBP 9,850 equals $12,903.50, reported as $12,904; SIPP GBP 31,200 equals $40,872; aggregate $62,815.
Year 5, assumed rate 1.19: current account GBP 5,400 equals $6,426; ISA GBP 12,600 equals $14,994; SIPP GBP 44,750 equals $53,252.50, reported as $53,253; aggregate $74,673.
Year 6, assumed rate 1.33: current account GBP 8,250 equals $10,972.50, reported as $10,973; ISA GBP 15,900 equals $21,147; SIPP GBP 57,300 equals $76,209; aggregate $108,329.

Year 2 is the year that catches people, and it is the reason a six-year reconstruction cannot be shortcut by looking only at the years that felt significant. The sterling balances barely moved between Year 1 and Year 2: the current account rose by GBP 100 and the ISA by GBP 150. What crossed the threshold was the exchange rate. A filer who reasons that nothing changed, so the threshold cannot have been crossed, has already made an error, and it is an error that only a year-by-year conversion at each year-end rate exposes. Note too that every account is reported in full in each filing year, including the current account in Year 3 at $6,375, because the test is aggregate value while the reporting is per account.

Which late filing reason code should you select?

The BSA E-Filing System does not simply ask for a free-text excuse. It presents a defined list of late filing reason codes, and two of them are purpose-built for a documentation problem. Selecting the code that actually fits is more credible than defaulting to Other. The list is:

A: Forgot to file
B: Did not know that I had to file
C: Thought account balance was below reporting threshold
D: Did not know that my account qualified as foreign
E: Account statement not received in time
F: Account statement lost (replacement requested)
G: Late receiving missing required account information
H: Unable to obtain joint spouse signature in time
I: Unable to access BSA E-Filing System
Z: Other

Codes F and G are the honest selections for the fact pattern this article describes, and they are better supported than Z because you can evidence them: a lost statement for which a replacement was requested is exactly what a dated subject access request to a UK bank demonstrates, and late receipt of missing required account information is exactly what an extension notice invoking electronic archiving demonstrates. Where the real reason is that you did not know the obligation existed, B or C is the accurate answer, and accuracy matters more than presentation.

If you select Z, a narrative explanation is required, and explanations for late filing are limited to 750 characters. Publication 5569 describes the same field as up to 750 characters within a text box to explain the late filing or indicate whether the filing is made in conjunction with an IRS compliance option. Seven hundred and fifty characters is roughly a tight paragraph, so draft it outside the system and edit it down before you paste it in. One selection is not discretionary at all: an FBAR filed as part of a streamlined submission must select Other as the reason for filing late, and enter Streamlined Filing Compliance Procedures in the explanation box. Tagging a streamlined FBAR with code F or G instead is a real processing error.

Can you file now and amend later?

Yes, and the IRS says so directly. The FBAR is due 15 April, and those who do not meet the April 15 due date must file by October 15, the automatically extended due date for the FBAR, as set out at https://www.irs.gov/newsroom/details-on-reporting-foreign-bank-and-financial-accounts. The same guidance tells filers who do not have all their information by the extended due date to file as complete a report as possible by October 15 and later amend the report when they have more information. There is no separate extension mechanism: extensions of time to file federal tax returns do not extend the time for filing an FBAR.

For a filer whose UK subject access request is still running against an October deadline, that is a decisive answer. File the reasonable approximation, then amend. One mechanical point catches people out: correcting a previously accepted FBAR means marking the Amendment Indicator, entering a new Date of Signature and completing all other applicable fields in their entirety. A FinCEN amendment is a full re-filing, not a partial patch, so keep the original workpapers in a form you can rebuild from rather than assuming you can adjust a single figure later.

How does the reconstruction file support the Form 14653 certification?

The Streamlined Foreign Offshore Procedures require Form 14653, certifying that the failures resulted from non-willful conduct, which for these purposes means conduct that is due to negligence, inadvertence, or mistake. Taxpayers under civil examination or criminal investigation are ineligible, and the non-residency test requires that in one of the most recent three years for which the return due date has passed, the individual did not have a US abode and was physically outside the United States for at least 330 full days.

The reconstruction file is the evidence base for that certification. A dated log of every statement request sent, every subject access request and its acknowledgement, every bank refusal or partial response, every extension notice invoking archived data, and any ICO escalation is contemporaneous documentary proof of good-faith effort. It converts a narrative assertion of non-willfulness into something a reviewer can test. Assemble the log as you go, not retrospectively, because a log created after the fact reads exactly like a log created after the fact.

Do both holders of a joint UK account report the full balance?

Each holder with a financial interest reports the account, and the maximum value reported is the maximum value of the account rather than a half share. That creates a reconstruction problem specific to cross-border couples. A UK institution handling a data request on a jointly held account will take care over releasing data that also relates to the other holder, and a non-US spouse may have entirely legitimate objections to their financial history entering a US filing package. Where the joint holder is a non-US person, resolve the data question first: request the account-level data you are entitled to, and be prepared for the institution to redact or withhold material relating solely to the other holder.

If spouses do file a single joint FBAR, they must complete and sign FinCEN Form 114a, the Record of Authorization to Electronically File FBARs, which is maintained with the filer's records rather than filed with the report. Note also that reason code H exists precisely for the case where a joint spouse signature could not be obtained in time, which is a real answer for a couple where one spouse is abroad or unwilling to sign to a deadline.

What records must you keep, and how long does the exposure run?

31 CFR 1010.420 requires five specific data points for each account: the name in which the account is maintained, the number or other designation identifying the account, the name and address of the foreign financial institution, the type of account, and the maximum value of each account during the reporting period. Those records must be kept five years from the due date of the report, which is 15 April of the year following the calendar year being reported, and keeping a copy of the filed FBAR can help to satisfy the recordkeeping requirements. Filers reporting 25 or more accounts may omit per-account detail from Parts II to V, but detailed information about each account, including all information called for on the report, must be recorded and retained, and produced if FinCEN or the IRS asks. An officer or employee who files solely to report signature authority over an employer's foreign account is not required to personally retain records regarding those accounts.

On penalties, be precise rather than dramatic. Non-willful and negligent civil penalty maximums are not fixed in statute; they are inflation-adjusted annually and set out in the Penalty Adjustment Table at 31 CFR 1010.821, so any article quoting you a fixed current figure is quoting a number with a shelf life. For historical context, for violations occurring on or before 2 November 2015 the non-willful penalty was capped at $10,000 per violation where not due to reasonable cause, and the willful penalty at the greater of $100,000 or 50% of the account balance at the time of the violation. Willful penalties under 31 USC 5321(a)(5)(C) remain up to the greater of the amount in 31 CFR 1010.821 or 50% of the amount in the account at the time of the violation, and criminal exposure for failure to file an FBAR or retain required records runs to $250,000 or five years or both under 31 USC 5322(a), rising to $500,000 or ten years or both where other laws are also violated. None of that is engaged by a reasonable-cause late filing that properly reports the account.

The mistakes that turn a fixable missed FBAR into a problem

Waiting for complete statements before filing, when the IRS expressly permits filing as complete a report as possible and amending later
Reporting the year-end balance instead of the highest value reached during the year
Converting at the date of the peak, or at an average rate, instead of the year-end Treasury rate for each year separately
Rounding down, or reporting cents, instead of rounding up to the next whole dollar
Omitting accounts that were individually small, when the test is aggregate value and the reporting is per account
Leaving ISAs, SIPPs, e-money accounts and platform nominee accounts off the inventory
Ticking Item 15a as a general fallback rather than for a genuinely undeterminable account
Tagging a streamlined FBAR with a substantive reason code instead of Other plus the words Streamlined Filing Compliance Procedures
Treating an amendment as a partial correction rather than a full re-filing with a new signature date
Following guidance that still names a withdrawn IRS procedure as a live route

A missed FBAR is a documentation problem before it is a penalty problem, and it is solved in that order: fix the account inventory, open the UK record requests, build the workpapers, convert year by year, file, then amend. The FinCEN filing portal is at https://www.fincen.gov/report-foreign-bank-and-financial-accounts, and the FBAR Reference Guide that governs most of the judgement calls above is Publication 5569 at https://www.irs.gov/pub/irs-pdf/p5569.pdf. If the missed FBARs sit alongside missed or understated US returns, the reconstruction feeds a streamlined package rather than a standalone filing, and we set out that preparation work at us-uktax.com/irs-streamlined-filing and us-uktax.com/cross-border-tax-planning.