Is cash on a UK investment platform a deposit account or a custodial account on Form 8938?

In most cases it is part of the custodial account. The cash is client money the platform holds for you alongside the securities it custodies, under one account number and one contract, so it is reported within that custodial entry rather than as a separate deposit. Where the provider also offers a distinct cash savings product with its own reference and terms, that is a separate account and may be a deposit account in its own right.

Do I have to report the individual funds and shares held on the platform as well as the account?

No. The IRS confirms that where you have an interest in a financial account holding specified foreign financial assets, you do not separately report the assets inside that account on Form 8938. Report the account itself in Part I. Assets that are not held in a financial account, such as shares held directly on a company register, are reported individually in Part II instead. Reporting both duplicates value and misstates your asset base.

Does filing Form 8938 mean I do not need an FBAR for the same platform cash?

No. The IRS states plainly that filing Form 8938 does not relieve you of the separate FBAR requirement. They go to different agencies, use different thresholds and different mechanics. The FBAR applies where your foreign accounts exceeded 10,000 dollars in aggregate at any time in the calendar year and is filed through FinCEN's BSA E-Filing System, never attached to your return. Most platform holders owe both.

Does an ISA wrapper protect the cash from US reporting?

No. The ISA is a UK tax wrapper with no US recognition and no treaty protection. A cash ISA, a stocks and shares ISA and an innovative finance ISA are all financial accounts maintained by a foreign financial institution for these purposes. Interest credited inside an ISA is tax free in the UK and fully taxable in the US, and the account itself is reportable on both Form 8938 and the FBAR where the relevant thresholds are met.

Which institution do I name if my platform holds my cash at a different bank?

Name the platform. Under the FCA client money rules a firm segregates client money at approved banks and spreads it across institutions, but those sweep banks are the platform meeting its own obligations, not accounts of yours. The exception is a cash hub that opens an account in your own name at a named partner bank. Read the terms: if a bank owes the money to you directly, it is a separate reportable account.

How many years do I have to correct if I missed the platform account for several years?

Under the Streamlined Filing Compliance Procedures you file delinquent or amended returns for the most recent three years for which the due date has passed, with all required information returns attached, plus delinquent FBARs for the most recent six years for which the FBAR due date has passed, and a Form 14653 certification of non-willfulness. Where only the FBAR was missed, late FBARs go through the BSA E-Filing System with a reason for late filing.

UK Platform Cash Balances and Form 8938 Reporting

Missed reporting investment account Form 8938 problems almost always begin at the same line of the same statement: the cash balance sitting on a UK investment platform alongside the funds and shares. The short answer is that platform cash forms part of a financial account maintained by a foreign financial institution, it belongs in Part I of Form 8938, and the same cash is very likely reportable on the FBAR as well. The hard part is never whether to report it. The hard part is deciding what the account actually is, which institution to name against it, and what number to put in the value column, because a wrap or platform statement blends a client money cash balance with custodied securities in a way that neither form was drafted to accommodate.

In the returns we prepare for US persons living in the United Kingdom, the securities on a platform are usually picked up. The uninvested cash is the line that disappears. It disappears because it does not feel like a bank account, because it is often small at the year end and enormous in the middle of the year, and because the platform brand on the statement is not necessarily the institution holding the money. Every one of those instincts is wrong for US reporting purposes, and each of them produces a different failure. This article deals only with that cash line and with the reporting that surrounds it.

Why does UK platform cash get missed on Form 8938 in the first place?

The cash on a platform is functionally invisible. It is created by events, not by decisions: a dividend lands, a fund is sold, a subscription is made in April and sits uninvested until a model portfolio rebalances, a corporate action pays out. None of those feel like opening an account. The reader who is scrupulous about disclosing a current account at a UK high street bank will often not think of the four figure or six figure sum resting on a dealing platform as an account at all.

The platform statement leads with a total portfolio valuation, so the cash line is a sub-total buried inside a larger number rather than a balance in its own right.
Cash inside an ISA carries no UK tax consequence, so nothing on the UK side ever prompts the question.
Uninvested cash is frequently at its lowest on 31 December, which is exactly the date the reader checks.
Where the platform sweeps client money to third party banks, the reader has no obvious institution to name and quietly drops the entry.
Software driven from a single foreign account questionnaire tends to record one account per platform, which understates both the count and the value where the platform runs a separate cash product.

The consequence is asymmetric. An omitted cash balance rarely changes the tax by much, because interest on platform cash is modest. It changes the information return position completely, and information return exposure under section 6038D is where the cost sits. The IRS sets out the penalty architecture in the Form 8938 instructions at https://www.irs.gov/instructions/i8938, which describe a 10,000 dollar failure to file penalty, further penalties for continued failure after notification, and a 40 percent accuracy related penalty on any understatement attributable to an undisclosed foreign financial asset.

Is platform cash a deposit account, a custodial account, or something else?

Form 8938 does not offer one box for foreign accounts. Part I splits foreign deposit and custodial accounts into two separate counts and two separate value totals, and Part II is reserved for other specified foreign financial assets that are not held in a financial account. Getting the cash into the correct one of those three places is the first real task, and it is a classification exercise before it is a reporting exercise.

A deposit account is, in substance, a banking relationship: money placed with a bank or similar institution which owes it back to the depositor. A custodial account is an account in which a person holds financial assets for the benefit of another. Cash held on a dealing platform pending investment normally sits inside the custodial relationship. It is client money held by the platform for the client, alongside the securities the platform custodies for that same client, under one account number and one contract. In the returns we prepare, that cash is therefore reported as part of the custodial account rather than being carved out as a separate deposit account.

That default is not universal. Where the same provider also offers a distinct cash savings product with its own reference number, its own terms and its own interest rate, that is a different account and it is capable of being a deposit account in its own right. The distinction matters because Part I asks for the number of accounts in each category, not merely a total value. Reporting one custodial account where the reader in fact holds a custodial account and a separate cash account produces a return that is wrong on its face even if the aggregate value happens to be right. The IRS treatment of financial accounts is set out at https://www.irs.gov/businesses/corporations/basic-questions-and-answers-on-form-8938.

Which institution do you name when the platform sweeps the cash to another bank?

This is the question competitors skip, and it is the one that most often stalls a reconstruction. A UK platform does not keep client cash on its own balance sheet. Under the FCA client money regime at https://www.handbook.fca.org.uk/handbook/CASS/7/, client money must be segregated and placed with approved banks, and firms are expected to spread it across institutions rather than concentrate it with one. A single platform cash balance may therefore be physically held across several ring-fenced banks that the client has never chosen and may never have been told about by name.

The reporting answer follows the account relationship rather than the plumbing. The account is maintained for the client by the platform, the client contracts with the platform, and the platform is the foreign financial institution named on Form 8938 and on the FBAR. The downstream sweep banks are the platform meeting its own regulatory obligations; they are not separate accounts of the client and should not be listed as such. Listing them inflates the account count and creates a mismatch against any information the IRS receives under FATCA.

There is one important exception. Some cash hub arrangements do not sweep client money at all. Instead the provider introduces the client to a partner bank and an account is opened in the client's own name at that bank, with the platform acting only as an interface. Where that is what the paperwork says, the client holds a genuine second account at a second institution, and it is separately reportable and separately counted on both forms. The test we apply is simple: read the terms and identify whose name is on the account and who owes the money back. If the answer is a named bank rather than the platform, it is a separate account.

Does reporting the account mean the securities inside it are reported as well?

No, and this is where misclassification does its real damage. The IRS is explicit that where you have an interest in a financial account that holds specified foreign financial assets, you do not have to report the assets held in that account separately. Report the account; do not itemise the funds, shares and cash inside it as individual Part II entries. That guidance sits at https://www.irs.gov/businesses/corporations/basic-questions-and-answers-on-form-8938.

The mirror image is equally important. Specified foreign financial assets that are not held in a financial account are reported individually in Part II. So a shareholding held directly on a company register, outside any platform, is its own line, while the same shareholding moved onto a platform is subsumed into the account entry. Misclassifying in one direction duplicates value and inflates the reader's apparent foreign asset base; misclassifying in the other direction omits an asset entirely. Both are wrong, and only one of them is obvious on the face of the return.

Does Form 8938 replace the FBAR for the same platform cash?

It does not, and this is the single most frequently missed point in this whole area. The IRS states directly that filing Form 8938 does not relieve you of the separate requirement to file the FBAR if you are otherwise required to do so. The two regimes are compared side by side at https://www.irs.gov/businesses/comparison-of-form-8938-and-fbar-requirements, and the practical differences are wider than most readers expect.

Different agencies. Form 8938 goes to the IRS attached to the income tax return. The FBAR, FinCEN Form 114, goes to the Financial Crimes Enforcement Network.
Different thresholds. The FBAR applies where the aggregate value of foreign financial accounts exceeded 10,000 dollars at any time during the calendar year. Form 8938 applies only above much higher thresholds that vary by filing status and by whether the taxpayer lives abroad.
Different tests. Form 8938 has two threshold tests, one measured on the last day of the tax year and one measured at any time during the year. The FBAR has a single any-time aggregate test.
Different mechanics. The FBAR is filed electronically through FinCEN's BSA E-Filing System at https://bsaefiling.fincen.gov/ and never with a tax return.
Different deadlines in practice. The FBAR is due 15 April with an automatic extension to 15 October; Form 8938 follows the due date of the return it is attached to, including extensions.

Because the thresholds diverge so sharply, there are years in which a reader owes an FBAR and no Form 8938 at all. The IRS thresholds at https://www.irs.gov/businesses/corporations/do-i-need-to-file-form-8938-statement-of-specified-foreign-financial-assets require an unmarried taxpayer living abroad to hold more than 200,000 dollars of specified foreign financial assets on the last day of the tax year, or more than 300,000 dollars at any time during the year, before Form 8938 is triggered; for married filing jointly living abroad the figures are more than 400,000 dollars and more than 600,000 dollars. Living in the United States the figures are far lower, at more than 50,000 dollars and more than 75,000 dollars for an unmarried filer and more than 100,000 dollars and more than 150,000 dollars for a joint return. A platform cash balance of 30,000 pounds is an FBAR item every time and a Form 8938 item only if the wider asset base clears one of those tests. Readers who assume the forms move together get one of the two wrong.

Do the ISA, Innovative Finance ISA and general investment account wrappers change anything?

For US purposes the wrapper changes nothing at all. GOV.UK describes the range at https://www.gov.uk/individual-savings-accounts, covering the cash ISA, the stocks and shares ISA, the innovative finance ISA and the Lifetime ISA, with a maximum of 20,000 pounds that can be saved across ISAs in the 2026 to 2027 tax year. That envelope is a creature of UK law. The United States does not recognise it, no treaty article shelters it, and the account inside the wrapper remains a financial account maintained by a foreign financial institution.

The innovative finance ISA deserves a specific mention because its cash line behaves differently. Money awaiting deployment into peer to peer loans, and capital and interest repaid as loans amortise, can leave large uninvested balances cycling through the account for months. That cash is still cash held on a platform, still reportable, and the repayment cycle makes the intra-year maximum considerably higher than any quarter end snapshot suggests. A general investment account raises the same reporting questions with none of the UK shelter, which is why a GIA and an ISA on the same platform are frequently two separate account numbers and therefore two separate entries.

How do you value platform cash for two forms that ask different questions?

Form 8938 asks for the maximum value during the tax year of each specified foreign financial asset, and the instructions permit reliance on periodic account statements unless you know they do not reflect a reasonable estimate of the maximum value. Foreign currency amounts are translated using the exchange rate on the last day of the tax year published by the Treasury Bureau of the Fiscal Service. The FBAR likewise asks for the maximum value during the calendar year, and the record keeping guidance at https://www.irs.gov/businesses/small-businesses-self-employed/report-of-foreign-bank-and-financial-accounts-fbar requires records of that maximum value to be kept for five years.

The trap is the permission to rely on periodic statements. On a platform, cash spikes between statement dates. A rebalance executed in May can leave a very large cash balance for eleven days before the buy side settles, and no quarter end statement will ever show it. A reader who takes four quarterly cash figures and reports the highest of them has complied with the letter of a rule while producing a number that is materially too low. Where transaction data is available, and on a platform it always is, the defensible figure comes from a running cash ledger rather than from statement snapshots. That is the difference between a schedule that survives examination and one that merely looks tidy.

What about the UK funds and investment trusts sitting next to the cash?

Almost everything held alongside the cash on a UK platform is a passive foreign investment company. A foreign corporation is a PFIC where 75 percent or more of its gross income for the year is passive, or where at least 50 percent of the average percentage of its assets are held for the production of passive income, as set out at https://www.irs.gov/instructions/i8621. A UK domiciled OEIC or unit trust fails that test comfortably. A UK investment trust is a closed ended listed company whose business is holding investments, and it fails it too. The cash line is very often the only part of the account that is not a PFIC.

Here is the point that the comparison guides never make. The Form 8938 rule that you do not separately report assets held inside a reported account is a Form 8938 rule and nothing more. It does not switch off Form 8621. A separate Form 8621 is generally required for each PFIC, driven by distributions, dispositions and elections, entirely independently of the fact that the account holding those funds already appears in Part I. Form 8938 does contain a mechanism for acknowledging assets reported on other forms, but that mechanism reduces duplication on Form 8938; it never reduces the underlying obligation to file the other form. Readers who reason that the platform account is on Form 8938 and therefore the funds are dealt with have missed an entire filing stream, and the excess distribution regime, which bites where a current year distribution exceeds 125 percent of the average of the prior three years, will compound that error every year the holding is retained.

How is interest credited on platform cash taxed and translated?

Interest credited on a platform cash balance is ordinary income for US purposes in the year it is credited, whether or not any document is issued, whether or not it is reinvested, and whether or not the account sits inside an ISA. It belongs on the interest schedule of the return, and the foreign account questions on that schedule are themselves part of the disclosure package. Translation follows the general rule at https://www.irs.gov/individuals/international-taxpayers/foreign-currency-and-currency-exchange-rates, which is to use the exchange rate prevailing when the item is received, paid or accrued, with the Treasury Bureau of the Fiscal Service rates as the standard source.

The UK position is different in every respect and this is where preparers go wrong. Interest inside an ISA carries no UK tax. Interest in a general investment account is taxed against the Personal Savings Allowance described at https://www.gov.uk/apply-tax-free-interest-on-savings, which gives 1,000 pounds to a basic rate taxpayer, 500 pounds to a higher rate taxpayer and nothing to an additional rate taxpayer. Our readers are usually in the last of those bands, so every pound is taxed in the UK and every pound is taxed in the US, and the double tax relief has to be computed rather than assumed. Worse, any figure the platform produces is aligned to the UK tax year running from 6 April to 5 April. That certificate cannot be dropped into a US return covering a calendar year. The interest has to be rebuilt from the credited amounts, month by month, at the rate prevailing when each credit arose.

How do joint accounts and a non-US spouse change the position?

Joint holdings are a reliable source of understatement because readers instinctively halve. Form 8938 does not work that way. Where the account is jointly owned with someone other than a spouse, each owner includes the full value of the asset. Where spouses file separate returns, each spouse reports the entire value of a jointly owned account on that spouse's own Form 8938. Only spouses filing a joint return report the account once on a single form. The instructions at https://www.irs.gov/instructions/i8938 set the mechanics out in detail.

The common UK pattern is a US citizen married to a British spouse who is not a US person. That spouse has no US filing obligation of their own, and the household frequently concludes that a jointly held platform account is somehow half outside the system. It is not. The US spouse has a financial interest in the account and reports it, and the reporting value is not reduced to reflect the non-US spouse's share. Where the US spouse also has authority over an account held solely in the non-US spouse's name, the FBAR signature authority questions have to be answered on their own terms, separately from ownership. These are fact-specific determinations and they should be settled from the account documentation before any schedule is built.

A worked illustration: four years of platform cash

The following is an illustration only, and every figure in it is assumed rather than drawn from a real case. Assume a US citizen living and working in London, filing as a single taxpayer, holding a general investment account and a stocks and shares ISA on the same UK platform, with total specified foreign financial assets otherwise well below the Form 8938 thresholds. Assume an exchange rate of 1.27 US dollars to the pound throughout, purely as a stated assumption for the illustration; a real engagement uses the published Treasury rate for each year.

In the year in question the reader sold a fund holding in September and did not reinvest for three weeks. The GIA cash balance, which was 4,000 pounds at each quarter end, peaked at 210,000 pounds during that gap. The ISA cash balance peaked at 6,000 pounds. At 31 December the GIA cash line read 3,900 pounds. Using the assumed rate, the intra-year maximum across the two accounts is approximately 274,320 US dollars, while the 31 December cash position is approximately 4,953 US dollars. On those assumed facts the FBAR is unquestionably due, because the aggregate exceeded 10,000 dollars at a point in the year, and it must report the maximum value rather than the closing value. Whether Form 8938 is due turns on the whole asset base measured against both threshold tests, and the September spike may well carry the reader over the any-time test even though the last-day test is nowhere near being met.

The instructive part of the illustration is what a quarterly-statement approach would have produced. It would have reported a maximum of 4,000 pounds, roughly 5,080 US dollars, understating the true maximum by a factor of more than fifty and, on these assumed facts, potentially suppressing a Form 8938 obligation altogether. Nothing about that error is visible on the face of the statements. It is visible only in the transaction ledger.

How do you correct missed years?

Where returns were filed but income was omitted and the information returns were not attached, and where the failures were non-willful, the Streamlined Filing Compliance Procedures at https://www.irs.gov/individuals/international-taxpayers/streamlined-filing-compliance-procedures are the established route. They call for delinquent or amended returns for the most recent three years for which the due date has passed, with all required information returns attached, delinquent FBARs for the most recent six years for which the FBAR due date has passed, and a signed certification on Form 14653 setting out the facts supporting non-willfulness. The foreign offshore version of the procedures carries no miscellaneous offshore penalty for taxpayers who meet the non-residency requirement, which is why establishing the residency history is the first step, not an afterthought.

Where the income was reported correctly all along and only the FBAR was missed, the position is narrower. Late FBARs are filed through FinCEN's BSA E-Filing System, entering a reason for late filing in the form itself. Be careful with older guidance found online here: the IRS withdrew the page that described a named delinquent FBAR submission procedure, so any article presenting that as a live route is out of date and should not be relied on. The mechanism that remains is the one described in the FBAR instructions and in the IRS guidance at https://www.irs.gov/businesses/small-businesses-self-employed/report-of-foreign-bank-and-financial-accounts-fbar.

Choosing between the routes is a judgement about the facts, not a preference. If the omitted platform cash also carried omitted interest, or if PFIC funds in the same account generated distributions or disposals that were never reported on Form 8621, the correction is an income correction and the streamlined route is usually the correct frame. If the only defect is the information return, the analysis is different. Making that call before anything is filed matters, because a piecemeal submission can foreclose the better option.

How do you build a defensible schedule from platform statements?

A schedule is defensible when a reviewer can reproduce every figure from source documents without asking a question. On a platform that means rebuilding the cash line rather than transcribing it.

Pull the full transaction history for every account number on the platform, not the valuation statements, and separate the cash ledger from the holdings ledger.
Identify each distinct account number as its own reportable account, so a GIA, an ISA and any separate cash product are counted separately in Part I.
Read the account terms to establish whether the platform holds the cash as client money or whether a partner bank holds it in the client's own name, and name the institution accordingly.
Compute the running cash balance day by day and record the intra-year maximum with the date on which it occurred.
Translate the maximum at the published Treasury rate for the relevant year end for the information returns, and translate each interest credit at the rate prevailing when it was credited for the income schedules.
Flag every fund, OEIC and investment trust in the account for separate PFIC analysis, and confirm whether a Form 8621 is required for each one.
Retain the ledger, the statements and the working file for at least the five year FBAR record period, and longer where a streamlined certification has been signed.

The failure mode we see most often is not dishonesty and it is not complexity. It is a reader who reported the visible half of a platform account for years, in good faith, and never realised that the cash line was a separate reporting object with its own institution, its own value test and its own form. Once that is understood, the fix is mechanical. The schedule is built from the ledger, the classification follows the account terms, both forms are prepared from the same underlying data, and the position becomes stable for every year that follows.