Notice CP15: What the Letter Means and Why the Clock Matters
Notice CP15 is the letter that assesses a civil penalty against you, and when it concerns an unfiled foreign account report it deserves an immediate response rather than a considered one. The notice is not a proposal or a warning. It records a penalty that has already been assessed against your account, and it starts a 30-day window that governs everything you can do next.
Wealthy Americans in Britain receive these notices more often than the numbers suggest, because the reporting obligation attaches to ordinary current accounts and brokerage portfolios. Consequently, a filer who considers themselves entirely compliant on income tax can still face a five-figure or six-figure assessment.
This guide explains exactly what the notice does, how the response process works, and the several ways in which foreign account penalties differ from every other tax dispute you may have encountered. Furthermore, it covers the practical problem that no American guidance addresses: the 30-day clock running while the letter crosses the Atlantic. At TaxYork, we prepare protest submissions and the underlying records for British-resident clients, so what follows reflects live casework.
What Notice CP15 Actually Is
Notice CP15 is an assessment document. It identifies the penalty, the statutory provision under which it arises, the amount, and the date by which payment is expected. Additionally, it explains in brief terms how to dispute the charge.
Understanding the category matters enormously. Specifically, this is an assessable penalty, which means the agency may assess it directly without first issuing a deficiency notice and without giving you a pre-payment route to the Tax Court. That single feature shapes every option described below.
You may also encounter related notices. Notably, a variant covering certain other penalties exists, and the guidance on the CP15B notice illustrates the same structure. Therefore, identifying precisely which penalty your Notice CP15 assesses is the essential first step.
The Letters That Should Have Come First
A Notice CP15 rarely arrives without warning, and the earlier correspondence matters to your position. In a foreign account examination, the agency typically issues a proposed penalty letter first, giving you 30 days to submit a written protest to the examiner.
If that earlier letter reached you and went unanswered, the assessment follows. Conversely, if it never arrived, that fact is itself relevant, because it may support a request to reconsider the assessment on procedural grounds.
British readers should check the address on every document. Furthermore, an examination letter posted to a superseded American address explains a great many assessments that clients believe arrived from nowhere. Accordingly, we always reconstruct the correspondence trail before drafting any response to a Notice CP15.
The 30-Day Window and the Atlantic Problem
The Notice CP15 response period runs from the date printed on the notice rather than the date you received it. That distinction is trivial for a taxpayer in Ohio and serious for one in London.
International post routinely consumes a fortnight. Consequently, a notice dated the first of the month may reach a Kensington letterbox on the sixteenth, leaving half the window gone before you have read the first line. Moreover, if you were travelling, the remaining time can disappear entirely.
Treat the arrival date as an emergency rather than an inconvenience. Additionally, requesting an extension in writing at the outset is frequently possible and always better than missing the date. In short, the single most damaging response to a Notice CP15 is to set it aside until the weekend.
Why an FBAR Penalty Is Not an Ordinary Tax Dispute
This section contains the Notice CP15 point that catches out even sophisticated filers, and most general penalty guidance omits it entirely. Foreign account penalties live in a different body of law from your income tax.
Title 31 Rather Than Title 26
The reporting obligation arises under section 5314 of Title 31, which forms part of the Bank Secrecy Act rather than the Internal Revenue Code. The penalty provisions sit alongside it in section 5321.
That placement has real consequences. Specifically, the report is a FinCEN form that the agency administers on FinCEN's behalf, and it is not a tax return. Furthermore, the amounts assessed are not taxes, notwithstanding that a tax examiner assessed them.
Everything downstream follows from this. Therefore, procedures you may associate with tax disputes, including deficiency notices and Tax Court petitions, simply do not apply to the penalty your Notice CP15 assesses.
No Tax Court Jurisdiction
The Tax Court hears disputes arising under the Internal Revenue Code, which a Notice CP15 for a foreign account penalty does not. Because a foreign account penalty arises under a different title, that court has no jurisdiction, and there is no petition to file.
This surprises almost everyone. Specifically, clients who have read general guidance about ninety-day letters and Tax Court petitions arrive expecting a familiar route, and the route does not exist. Consequently, waiting for a deficiency notice that will never come wastes the window that does matter.
The practical implication is straightforward. Moreover, your realistic forums are the agency's own appeals function and, ultimately, the federal courts. Accordingly, the administrative response to a Notice CP15 carries far more weight than it would in an income tax matter.
The Assessment and Collection Timeline
Two separate periods govern the agency's position, and confusing them causes unnecessary alarm. The assessment period runs six years from the date the report was due, which is why examinations characteristically cover a six-year span.
Collection operates differently again. Once assessed, the government has a statutory window in which to bring a civil action to reduce the penalty to judgment, and that action is brought by the Department of Justice rather than by the agency itself.
Delay therefore carries a specific cost. Furthermore, unpaid amounts attract interest and additional charges under the federal debt collection provisions, which include a further penalty on amounts left delinquent. In short, ignoring a Notice CP15 converts a fixed sum into a growing one.
The Reasonable Cause Defence and Its Hidden Second Limb
Most guidance on a Notice CP15 describes reasonable cause as though it were a single test. The statute is more demanding than that, and the second requirement defeats a surprising number of otherwise strong cases.
The Two-Part Statutory Test
The non-willful penalty provision contains an express exception. No penalty applies where the violation was due to reasonable cause, and where the amount of the transaction or the balance in the account was properly reported.
Read that conjunction carefully. Specifically, both limbs must be satisfied, so a compelling explanation for the failure does not by itself defeat the penalty if the reporting limb is unmet. Consequently, the exception is narrower than the phrase reasonable cause implies.
The second limb is heavily contested. Additionally, the interaction between never having filed at all and the requirement that the balance be properly reported has produced genuine litigation. Therefore, framing the argument against a Notice CP15 requires addressing both limbs explicitly rather than only the sympathetic one.
What Actually Constitutes Reasonable Cause
The standard behind a Notice CP15 challenge asks whether you exercised ordinary business care and prudence. It is a facts and circumstances test, and the quality of the evidence matters more than the eloquence of the narrative.
Certain patterns recur in successful submissions. Specifically, reliance on a qualified professional who was given full information and never raised the obligation carries real weight, particularly where an engagement letter and correspondence evidence the relationship. Moreover, serious illness, bereavement or a documented incapacity during the relevant period are recognised.
British circumstances add credible material. Furthermore, a relocation package that addressed only United Kingdom compliance, or a British accountant who prepared self assessment returns without ever mentioning American reporting, describes a common and genuinely innocent reality. Accordingly, these facts belong in the response rather than in a covering note.
Evidence That Persuades
Assertion is not evidence, and a protest built on adjectives fails. The submission should attach the documents that establish the narrative rather than describing them.
Useful material is more mundane than clients expect. Specifically, engagement letters, the questionnaires your preparer sent you, relocation documentation, medical records where relevant, and the account opening paperwork all support the account of events. Additionally, a clear chronology stating what you knew and when you knew it gives the reviewer a spine to follow.
Consistency across documents matters just as much. Therefore, we reconcile the protest against the returns, the reports and any earlier certification before it is filed, because an internal contradiction damages a response to a Notice CP15 more than a thin fact pattern does.
How the Response Process Actually Works
Three practical stages follow a Notice CP15, and choosing well at each one shapes the eventual outcome. None of them requires you to travel to America.
Filing a Written Protest
The first response is a written protest addressed as the notice directs, submitted within the response window. It should identify the notice, the penalty and the years, then set out the factual and legal grounds on which you dispute the assessment.
Structure improves reception considerably. Specifically, a protest that opens with a short statement of the relief sought, follows with a chronology, then addresses each statutory limb in turn, is far easier for a reviewer to act on than a narrative letter. Furthermore, attaching a schedule of the accounts and balances demonstrates that the position is properly reconstructed.
Representation should be in place before filing. Additionally, Form 2848 puts a representative on record so correspondence can be handled without international post at every turn. Consequently, the practical handling of a Notice CP15 improves immediately once an authorisation is on file.
Escalating to the Independent Office of Appeals
Where the protest does not resolve matters, the Independent Office of Appeals offers a review by a function separate from the examiners who proposed the penalty. Appeals considers the hazards of litigation, which gives it latitude that an examiner does not have.
Preparation determines the value of that conference. Specifically, the guidance on preparing a request for appeals sets out what the submission should contain, and a well-evidenced file gives the officer something to work with.
Conferences run by telephone or video routinely. Moreover, that suits a British-resident taxpayer perfectly, because attendance in person is unnecessary. Therefore, distance is not a barrier to pursuing a Notice CP15 through appeals.
The Court Route and the Mendu Point
Litigation remains available if the administrative process fails, and here sits a genuine advantage that almost no expatriate guidance mentions. Ordinarily, a taxpayer must pay a disputed amount in full before suing for a refund.
Foreign account penalties have been treated differently. Notably, the Court of Federal Claims concluded in the Mendu litigation that the full payment rule does not apply to these penalties, precisely because they arise outside the Internal Revenue Code. Consequently, a taxpayer may pursue a challenge in that forum without first paying the assessment in full.
The government has its own route as well. Furthermore, where an assessment remains unpaid, the Department of Justice tax division may sue to reduce the penalty to judgment, which is the point at which enforcement becomes serious. Accordingly, the litigation posture around a Notice CP15 differs materially from an income tax dispute, and it should inform the strategy from the outset.
The Numbers Behind the Assessment
Checking the arithmetic on a Notice CP15 is not pedantry. Assessments do contain errors, and the correct figures have moved substantially in recent years.
Current Penalty Ceilings
The ceilings adjust annually for inflation, and much of the internet has not kept up. For penalties assessed on or after 17 January 2025, the non-willful maximum stands at $16,536 per violation, while the willful maximum is the greater of $165,353 or 50 per cent of the account balance at the time of the violation.
Compare those with the $10,000 and $100,000 figures still quoted widely. The understatement exceeds 60 per cent, which matters when you are checking whether an assessment is even arithmetically possible.
Mitigation guidelines also exist internally. Additionally, the Internal Revenue Manual provisions on foreign account reporting set out the mitigation thresholds examiners are expected to apply, and assessments occasionally depart from them. Therefore, testing your Notice CP15 against the manual is a worthwhile exercise.
The Bittner Per-Report Rule
One development substantially reduced exposure for multi-account filers. In Bittner v. United States, the Supreme Court held that the non-willful penalty applies per annual report rather than per account.
The arithmetic changes dramatically. Specifically, a London filer with eight British accounts across six years faces six potential violations rather than forty-eight, which converts a theoretical exposure of nearly $800,000 into one under $100,000.
Older assessments occasionally reflect the previous approach. Consequently, where a Notice CP15 appears to count accounts rather than reports, that is a concrete and checkable ground of challenge rather than a matter of judgement.
Willfulness and Why the Characterisation Dominates
The gulf between the two penalty categories dwarfs every other variable. A non-willful characterisation caps exposure per report, while a willful one exposes half the account balance.
Willfulness includes more than deliberate evasion. Notably, courts have accepted that reckless disregard and wilful blindness can satisfy the standard, which is why conduct such as correcting quietly without any certification attracts scrutiny.
The characterisation is therefore the main battleground. Furthermore, the evidence that supports non-willfulness is largely the same material that supports reasonable cause, so the two arguments are built together. Accordingly, we treat the characterisation as the primary objective when responding to a Notice CP15.
The British Dimension
American penalty guidance stops at the water's edge, which leaves London-based readers without answers to the questions they actually have.
No Relief Against Your UK Tax
Clients frequently ask whether the penalty reduces their British liability. It does not. A United States civil penalty is not a creditable foreign tax, and it is not a deductible expense against employment or investment income for HM Revenue and Customs purposes.
The cost is therefore borne entirely from post-tax funds. Specifically, settling a $99,216 assessment from sterling requires earning considerably more than that at British marginal rates, which changes the commercial calculation about whether to contest.
That arithmetic argues for early engagement. Moreover, the cost of preparing a strong protest is a fraction of the assessment in almost every case we handle. Consequently, the economics of challenging a Notice CP15 are usually compelling for a wealthy filer.
Whether HMRC Learns About It
A separate anxiety concerns disclosure. An American penalty assessment is not routinely reported to the British authorities, and the exchange of information between the two countries concerns account and income data rather than penalty files.
Nevertheless, the underlying facts may matter domestically. Specifically, if the same accounts generated income that was omitted from your British returns, a United Kingdom correction is required on its own footing, entirely separately from the American position.
Reviewing both sides together is therefore prudent. Additionally, our cross-border tax planning team assesses the British exposure at the same time, because discovering a domestic problem midway through an American protest is difficult to manage.
Practical Handling From a London Address
Distance creates friction that preparation removes when a Notice CP15 arrives. Correspondence deadlines assume domestic post, telephone lines run on American hours, and the international line is reachable on +1 267 941 1000 rather than any toll-free number.
Several measures help materially. Specifically, putting a representative on record removes the postal dependency, confirming your address of record prevents notices going astray, and the agency's international contact guidance sets out the current arrangements including fax routes for particular matters.
Escalation exists where matters genuinely stall. Furthermore, the Taxpayer Advocate Service can assist where a delay is causing real hardship and ordinary channels have failed. Therefore, a Notice CP15 received in London is manageable, provided the handling is organised rather than improvised.
Case Study: A £2.1 Million Portfolio and a Six-Year Assessment
Concrete facts show how a Notice CP15 response fits together. The following reflects a composite of engagements we have handled, with figures adjusted to protect confidentiality.
The Assessment
Consider Claire, a US citizen and company owner in London, UK-resident since 2014. She held a current account, two savings accounts, a stocks and shares ISA and a brokerage portfolio, with a peak aggregate value of roughly £2.1 million across the relevant years.
Her British tax affairs were immaculate and her American returns had been filed annually by a preparer who never asked about foreign accounts. However, she had never filed a single foreign account report, and an examination produced an assessment across six years.
The notice assessed $99,216, being six reports at the current non-willful ceiling. Additionally, it arrived at her London address eleven days after its date, leaving nineteen days of the response window.
What We Prepared
We filed an authorisation immediately so the correspondence could be handled directly, then requested a short extension in writing while the file was assembled.
The protest addressed both statutory limbs rather than only the sympathetic one. Specifically, we evidenced reliance on her preparer with the engagement letters and the annual questionnaires, none of which asked about foreign accounts, and we set out a chronology showing when she first learned of the obligation.
We also checked the arithmetic. Notably, the mitigation guidelines in the internal manual pointed to a lower figure given her compliance history, and the assessment had not applied them. Consequently, the submission raised a computational ground alongside the substantive one.
The Outcome and What Drove It
The matter resolved at appeals rather than in court. The officer accepted the non-willful characterisation, and the mitigation argument reduced the assessment substantially against the ceiling figure originally charged.
Two factors carried the weight. Furthermore, the documentary evidence of professional reliance was contemporaneous rather than reconstructed, and the arithmetic challenge gave the officer a principled basis to move.
The timing lesson was the sharpest. Ultimately, had Claire waited for the following weekend to open the envelope, the window would have closed, and the response to her Notice CP15 would have started from a far weaker position.
How TaxYork Can Help
We prepare US and UK returns and compliance submissions for wealthy Americans in Britain, and penalty responses sit within that work rather than outside it. Consequently, the team that reconstructs your account history also drafts the protest, which keeps the evidence and the argument aligned.
Our first step is practical. We put an authorisation on file, retrieve your account transcripts to establish exactly what has been assessed and when, and confirm the correspondence trail behind the assessment. Importantly, we do this before drafting, because assessments occasionally rest on letters that never reached you.
From there we build the submission. Our FBAR and FATCA compliance service reconstructs six years of balances and prepares any outstanding reports, while our US tax return preparation team corrects the underlying years where required. Additionally, where a catch-up remains outstanding, our IRS Streamlined Filing service addresses it alongside.
Fixed fees apply throughout, and we quote before work begins. Therefore, you know the cost of responding to a Notice CP15 against the assessment you are facing.
Conclusion
Notice CP15 records a penalty that has already been assessed, and the 30-day window it opens is the most valuable asset you have. Everything that follows, from the protest to appeals to any eventual litigation, is shaped by the quality of the response you file inside that period.
Three features distinguish these disputes from ordinary tax matters. The penalty arises under the Bank Secrecy Act rather than the Internal Revenue Code, the Tax Court therefore has no jurisdiction, and the full payment rule has been held not to apply, which preserves a court route without paying first. Furthermore, the statutory reasonable cause exception has two limbs, and a response addressing only the sympathetic one is incomplete.
The figures deserve checking as carefully as the argument. Specifically, the current ceilings of $16,536 and $165,353 have replaced the amounts most sources still quote, and the Bittner ruling counts reports rather than accounts. Ultimately, a Notice CP15 landing on a London doormat is a serious document with a short fuse, and the response you file in the first fortnight matters more than anything you do afterwards.
Contact Us
If a penalty assessment has arrived, act on the day it reaches you rather than at the weekend. The window is short, and the strength of the first submission shapes everything that follows.
Email hello@taxyork.com or telephone 020 3488 8606 for a confidential discussion. Alternatively, book a consultation directly, and we will review the notice, establish the correspondence trail and prepare the protest.
Disclaimer
This article provides general information about United States civil penalty procedures and does not constitute tax, legal or financial advice, and it is not a substitute for representation in a specific dispute. Penalty amounts, procedures and case law change, and the position described reflects August 2026. Furthermore, individual circumstances vary considerably, and the merits of any challenge depend entirely on the facts and the documentary evidence available. Accordingly, you should obtain professional advice tailored to your situation before responding to any assessment. General guidance for Americans abroad is available from the IRS on US citizens and resident aliens abroad, and the reporting requirement itself is explained on the IRS foreign bank account reporting page. TaxYork accepts no liability for any action taken or not taken in reliance on this content.
*Written by the TaxYork Expert Team — US-UK tax specialists. Email hello@taxyork.com or call 020 3488 8606.*