Introduction: What a CP49 Notice Means for Americans in Britain
A CP49 notice is the IRS telling you that it kept some or all of the refund on your latest return and used it to pay a balance you owe for a different tax year. For an American living in London, the letter usually arrives weeks late, in a plain envelope, and well after you had planned around the refund. Moreover, it often comes as the first sign that a missed US tax return, a penalty or an old assessment is still sitting on your IRS account.
Most guides treat the notice as a household matter of child support and student loans. In our experience, the clients who receive one in Britain look very different. They are bankers whose US payroll over-withholds tax on vesting shares, founders who filed late catch-up returns, and dual nationals whose UK tax wiped out their US bill but left a penalty behind. Consequently, the questions they need answered are about penalties, statutes and missed reporting, not household debts.
What the CP49 Notice Tells You in Plain Terms
The CP49 notice sets out three figures. It shows the overpayment on the return you just filed, the amount the IRS moved to the older year, and anything left over. According to the IRS guide to understanding your CP49, any remaining refund normally follows within about three weeks, unless another tax or debt absorbs it first.
The notice does not, however, explain why the older balance exists. That gap matters because the original balance may be wrong, may carry penalties you can remove, or may have expired. Therefore, the notice is a starting point for a review, not the end of the story.
Why Wealthy Americans Abroad See This Notice
Refunds are common among high earners in Britain for a simple reason. US employers and US brokers withhold American tax at source, yet the UK taxes the same income at up to 45%, and the foreign tax credit then removes most or all of the US liability. As a result, the return shows a large overpayment.
Meanwhile, the same clients often have an older year that went wrong. A return filed two years late, a net investment income tax bill the foreign tax credit could not cover, or an international information return penalty can all leave a debit. When the large refund meets the old debit, a CP49 notice follows almost automatically.
How the IRS Offset Works Under Section 6402
The legal power behind the notice is short. Internal Revenue Code section 6402 lets the IRS credit any overpayment against any internal revenue tax liability of the person who made it. Furthermore, the IRS does not need your consent, a court order or advance warning to do so.
The Order the IRS Follows
The Internal Revenue Manual chapter on refund offset research and reversals sets a strict sequence. Your overpayment goes first to outstanding federal tax debts, then to non-tax debts collected through the Treasury Offset Program, and only then to any credit you asked to carry forward. In practice, therefore, a federal tax balance on any year takes priority over everything else, which is why a CP49 notice usually arrives before any other offset letter.
Notably, the offset reaches assessed balances only. A year you never filed, and that the IRS has not assessed, cannot receive an offset, although the IRS may freeze the refund while it waits. That freeze is a separate process, which we explain in our guide to the IRS CP63 refund hold for missed returns.
Credit Elect Does Not Shield the Refund
Many Americans in Britain elect to roll an overpayment forward into next year's estimated tax. It feels safer, because the money never leaves the IRS. However, the manual is clear that the offset comes first. If you owe on an older year, the IRS satisfies that debt and applies only the remainder to the credit elect.
This catches clients out in the following January and June. Specifically, they assume the estimated payment covers the new year, yet part of it went to an old penalty, so they underpay and face a fresh estimated tax charge. A CP49 notice that mentions a reduced credit elect should therefore prompt an immediate check of your next estimated payment.
Interest on the Offset Amount
Interest works in your favour less than you might expect. Under section 6611, overpayment interest on an offset amount runs only from the date of the overpayment to the due date of the debt it pays. In addition, for the part the IRS actually refunds, no interest is due if the IRS pays within 45 days of the return's due date or filing date.
On the debit side, the older balance has been accruing interest at the underpayment rate. The IRS confirmed that rates stay at 7% for the fourth quarter of 2026, compounded daily, for individuals. Consequently, a balance left for two or three years can grow well beyond the original tax before any CP49 notice pays it off.
Where the Balance Came From: Missed Returns, SFRs and Penalties
Once you know an offset happened, the next question is what the older balance actually is. For Americans in Britain, we see three recurring sources, and each has a different fix.
Substitute for Return Assessments on Missed Years
If you missed US tax returns for several years, the IRS may have prepared a substitute for return using only the income it could see. Such an assessment ignores your UK tax, your foreign tax credit and often your filing status. Hence, it can show a large liability for a year in which you actually owed nothing.
A refund on a later year then quietly pays that inflated bill, and the CP49 notice is often the first you hear of it. The remedy is to file the real return for the missed year and ask the IRS to reconsider the assessment, as Publication 3598 on audit reconsideration explains. When the IRS accepts the return, it reduces the assessment, and the offset money becomes an overpayment that the IRS can refund or credit.
Late-Filing Penalties on Catch-Up Returns
The second source is a penalty on a return you did file, but late. The failure-to-file and failure-to-pay penalties reach 5% and 0.5% a month respectively, each capped at 25%. Even when the foreign tax credit leaves only a small net investment income tax bill, those percentages add up.
Importantly, many of these penalties are removable. Where your three prior years were clean, first-time abatement can remove both the filing and payment penalties for the year. Alternatively, reasonable cause relief may apply. Either way, even after a CP49 notice has confirmed the offset, the IRS returns the abated amount to the account, and because the offset already paid it, the result is a refund.
Information Return Penalties for UK Company Owners
The third source is specific to business owners. An American who owns a UK limited company must file Form 5471, and a late or missing form can attract a $10,000 penalty per form per year. These penalties are assessed like tax, so a later refund can pay them.
A CP49 notice that refers to a year with an unexpectedly round balance is often a sign of exactly this. Since the penalty is assessed rather than litigated, you can still ask for abatement on reasonable cause grounds after the offset. Therefore, an owner who simply accepts the notice may be leaving $10,000 or more on the table.
The FBAR Penalty Exception: Why Some Offsets Arrive Without a CP49
Not every seized refund produces a CP49 notice. This distinction confuses even experienced filers, and none of the generic guides we reviewed explains it for overseas taxpayers.
Treasury Offset Program and Title 31 Debts
Penalties for a missed FBAR, the foreign bank account report explained here by Investopedia, are not internal revenue taxes. They arise under Title 31 of the US Code, not the tax code, and the FinCEN FBAR filing guidance sits outside the Internal Revenue Code entirely. Accordingly, the IRS cannot use section 6402 to pay them. Instead, an unpaid FBAR penalty goes to the Treasury's Bureau of the Fiscal Service, which collects it through the Treasury Offset Program.
When that programme takes your tax refund, the Bureau, not the IRS, sends the notice. The IRS page on reduced refunds and debt offsets confirms the split. Moreover, a 2024 Tax Court decision held that FBAR penalties fall outside the collection due process rules that protect ordinary tax debts.
What to Do With a BFS Letter
If your letter comes from the Bureau of the Fiscal Service, the IRS cannot reverse it, so calling the number on a CP49 achieves nothing. Instead, you deal with the agency that referred the debt, or with the Bureau's offset call centre on 800-304-3107, a US toll-free line that may not connect from a UK phone. Furthermore, the IRS cannot issue a hardship bypass refund for a Treasury Offset Program debt.
Consequently, anyone with an outstanding FBAR penalty should expect every future US refund to disappear until the penalty is resolved. That is a strong reason to address missed FBAR and FATCA reporting before penalties are ever assessed, rather than afterwards.
How to Check and Challenge a CP49 Notice From the UK
Checking a CP49 notice takes an hour if your records are in order and several weeks if they are not. Living in Britain adds a practical layer, because post is slow and the IRS phone lines are hard to reach from abroad.
Reconcile Both Tax Years
Before replying to a CP49 notice, pull the account transcripts for both the refund year and the debit year from your IRS online account. The transcript shows the original assessment, every penalty, the interest and the offset itself, each with a date. Additionally, compare the debit year with the return you believe you filed, because a mismatch often reveals a substitute for return or a lost amended return.
If you cannot access the online account, the IRS international line on +1 267 941 1000 accepts calls from overseas, although it is not toll-free. Alternatively, a representative holding a Form 2848 power of attorney can call the practitioner line on your behalf, which is usually faster.
Disputes, Abatements and Audit Reconsideration
Once you know the source of the balance, choose the route that matches it. A substitute for return calls for the real return and audit reconsideration. A penalty calls for first-time abatement or a reasonable cause statement. Meanwhile, a payment the IRS failed to post calls for proof of payment, such as a bank confirmation of an international wire.
Timing also matters. The IRS generally treats an offset as a payment of the older year, so any refund claim for that year must satisfy the look-back limits in section 6511 and the refund window on missed returns. In practice, a claim filed within two years of the offset date normally preserves your right to the money.
Expired Collection Statutes
The IRS has ten years from assessment to collect a tax, under section 6502. An offset made after that period has expired is not valid collection. Instead, section 6401 treats any amount collected after the limitation period as an overpayment, which the IRS must refund.
Long-term expats are the group most exposed here. An assessment from 2014 or 2015 on a year you have forgotten can resurface when you finally file and claim a refund. Therefore, always check the assessment date on the debit year before accepting the offset shown on a CP49 notice.
Joint Returns With a British Spouse
If a CP49 notice follows a joint return with a British spouse who has their own income, the offset may take their share of the refund to pay a debt that is yours alone. In that case, your spouse can file Form 8379 for injured spouse allocation to recover their portion. We cover the mechanics in our guide to injured spouse relief for a British spouse.
Worked Example: A London Banker's $48,600 Refund
The figures below are illustrative, but they mirror the pattern behind most CP49 notice files we handle for US citizens working in the City.
The Facts
Daniel is a US citizen and managing director at a US bank in London. His restricted stock units vest through US payroll, which withholds federal tax at supplemental rates. In June 2026 he files his 2025 Form 1040 using the automatic extension for taxpayers abroad. Because UK tax at 45% supports a foreign tax credit that wipes out his regular US tax, the return shows an overpayment of $48,600.
However, Daniel had missed his 2022 return during a busy relocation year and filed it late in March 2025. That return showed $13,600 of net investment income tax on UK investment income, which the IRS does not let UK tax offset, and he never paid it. By the summer of 2026, the 2022 account carried the tax, a $3,400 failure-to-file penalty, $1,700 of failure-to-pay penalty and $2,410 of interest, a total of $21,110.
What the Offset Did
In August 2026, the IRS processed the 2025 return and applied $21,110 of the refund to 2022. A CP49 notice followed, showing the full overpayment, the amount applied and a remaining refund of $27,490. Because the IRS paid the balance more than 45 days after the return was filed, it also added a modest amount of overpayment interest.
Daniel had planned to roll the whole refund into 2026 estimated tax. Had he done so, only $27,490 would have reached his 2026 account, leaving his January payment short. As a result, the first step was to recalculate his 2026 estimates.
Recovering the Penalty
Daniel's 2019, 2020 and 2021 returns were filed on time with no penalties. He therefore qualified for first-time abatement on 2022. We requested abatement of both the $3,400 filing penalty and the $1,700 payment penalty, along with the interest charged on them, which came to about $600.
The IRS granted the request in October 2026. Because the offset had already paid those amounts, the abatement created a $5,700 credit on the 2022 account, which the IRS refunded with interest at 7%. In summary, Daniel recovered more than a quarter of the money the CP49 notice had taken, simply by asking the right question about the older year.
A Five-Question Review Before You Respond
We use the same short review for every client who forwards a CP49 notice, and it works equally well as a self-check.
Questions One to Three: Source, Accuracy and Age
First, ask which year on the CP49 notice received the money and what created the balance there: tax, a penalty or a substitute assessment. Second, ask whether that balance is accurate once you account for UK tax, the foreign tax credit and any payments you made. Third, check the assessment date, because anything older than ten years may sit outside the collection statute.
If any of those answers looks wrong, you have grounds to act. Otherwise, the offset is probably correct, and the review moves on to what you can still recover.
Questions Four and Five: Relief and Knock-On Effects
Fourth, ask whether any penalty in the balance qualifies for first-time abatement or reasonable cause relief, since an offset never closes that door. Fifth, look forward. Check whether the offset reduced a credit elect, whether a joint refund included your spouse's share, and whether other missed years or missed reporting, such as Form 8938, pension or ISA reporting, might produce further balances.
Finally, keep the notice, the transcripts and your workings together. The IRS will not send a second copy, and you may need the dates for a refund claim later.
How TaxYork Can Help
TaxYork prepares US and UK tax returns for high-net-worth Americans, dual nationals and business owners in Britain. When a client receives a CP49 notice, we obtain the transcripts under a power of attorney, rebuild the older year, and identify every penalty, assessment or statute point that can bring money back.
Where the balance stems from missed US tax returns, missed FBARs or missed UK returns, we prepare the full catch-up filing and choose the most suitable compliance route, including the IRS Streamlined Filing procedures where you qualify. In addition, we coordinate the US and UK returns, so the foreign tax credit and HMRC figures agree and future refunds are not lost to avoidable balances.
Conclusion: Treat the Notice as an Audit of Your Older Years
A CP49 notice is short and usually correct as arithmetic, yet it often hides a balance that should never have existed or penalties you can still remove. Consequently, the right response is not to file it away but to examine the year that received the money.
For Americans in Britain, the recurring causes are substitute assessments on missed years, late-filing penalties, information return penalties and, outside the CP49 system altogether, FBAR penalties collected through the Treasury. Each has a defined fix, and most fixes return money. Ultimately, a careful review costs far less than the refund you could otherwise lose.
Contact Us
If you have received a CP49 notice or a Treasury offset letter and want to know whether the older balance is right, book a consultation with our US-UK tax team. You can also email hello@taxyork.com or call 020 3488 8606. We will review both tax years, explain your options and prepare any returns or claims needed.
Disclaimer
This article provides general information about US federal tax collection and refund offset rules as understood in November 2026 and does not constitute legal or tax advice for your specific circumstances. The worked example is illustrative, and its figures and outcomes are not a prediction of any result. IRS procedures, interest rates and thresholds change, so please consult a qualified professional before acting, and refer to the IRS, the Taxpayer Advocate Service notice guide and HMRC for official guidance.