Figures relate to tax year 2025 (US)
You filed the return, nothing came back, and the refund looked smaller than you expected. Or larger.
A cross-border return can be wrong for years without the IRS ever writing to you, because most of the errors reduce a relief rather than understate income.
That is exactly why a second opinion on an expat return pays for itself more often than it does on a domestic one.
Key takeaways
- Cross-border errors rarely trigger a letter, so nothing tells you.
- The commonest mistakes cost you money rather than owing it.
- The exclusion and the credit are where most errors live.
- A P60 dropped straight onto a US return is a standing error.
- Three years back is usually still correctable.
- A review is cheaper than a year of filings.
- Bring the returns and the source documents, not just the returns.
- Not every mistake is worth correcting.
What is a second opinion worth?
In our practice a review finds something on a clear majority of expat returns prepared without a British counterpart. Usually it is a relief claimed badly rather than income missed. According to IRS guidance on choosing a tax professional, you remain responsible for everything on the return whoever prepared it.
Our guide to choosing a US-UK tax accountant covers who to use.
A clean review is worth something too.
What does a second opinion actually check?
Four things. Did you claim the better relief, and did the foreign tax land in the right year? Then, did somebody apportion British income into the American calendar, and did every reporting form actually go in?
Our guide to Form 1116 income baskets covers the credit.
The forms nobody filed are the expensive part.
Why does a return need a second opinion at all?
Because the IRS matches what it can see, and it cannot see a British payslip. A return claiming too little relief looks perfectly consistent to an automated check, so no notice is ever generated. Silence is not confirmation.
Our guide to IRS math error notices covers what the matching does catch.
Nobody writes to tell you that you overpaid.
What a review usually finds
| Finding | Typical effect | Correctable |
|---|---|---|
| Exclusion used where credit was better | Overpayment | Yes, three years |
| British tax credited in the wrong year | Timing error | Yes |
| P60 used without apportionment | Wrong income figure | Yes |
| Missing account or asset report | Penalty exposure | Yes, procedures exist |
| Pension treated as a foreign trust | Needless forms | Yes |
| No treaty position taken | Relief lost | Going forward |
Exclusion or credit, which was right?
It depends on the rates, and getting it backwards is the commonest finding of all. The exclusion covered up to $130,000 of earnings for 2025, which sounds generous until you set it beside British tax at 40% on the same money. Hardly anybody revisits the default choice.
Our guide to Form 2555 and the exclusion covers the claim.
Switching away from the exclusion has consequences, so model it first.
A worked example
Take an illustrative case. An American in London earns a good salary and her preparer claims the exclusion every year.
British tax on that salary far exceeds the American charge on the same income.
Claiming the credit instead would have left her with surplus credit to carry forward and a smaller bill.
She amended three open years, and the refund covered the review and the amendments with a good deal to spare.
How far back can a mistake be fixed?
Generally three years from filing for a refund claim, which usually means three open years at any moment. Some errors have longer windows, and an unfiled information return can leave a year open indefinitely. The three year rule is the practical limit.
Our guide to the statute of limitations covers the periods.
A year closes quietly, so a review has a deadline.
What does a second opinion cost?
Less than a year of filing, in most cases, because reading a finished return is faster than building one. A fixed fee for a defined scope is normal, and anybody charging by the hour for an open-ended look is not scoping it properly.
Our guide to streamlined filing costs covers fees generally.
Ask what the review covers before agreeing to it.
What should you hand over for a second opinion?
The last three American returns, the matching British returns, your P60s and payslips, and any notices you received. Returns alone are not enough, because the question is usually whether the figures on them were right in the first place.
Our guide to requesting a tax transcript covers the IRS record.
A transcript shows what the IRS actually holds for each year.
Do you have to tell your accountant?
No, and plenty of people do not until they know the answer. A review is a professional service like any other, and most good preparers take one calmly. Where a relationship has already soured, a quiet review first makes perfect sense.
Our guide to IRS power of attorney covers authority.
You own the return, whoever prepared it.
What if the preparer made the mistake?
The tax is still yours, which people find hard. A preparer's error does not shift liability for the tax itself, though it can support a penalty argument and in some cases a claim against them. The return carries your signature.
Our guide to reasonable cause relief covers penalty arguments.
Reliance on an adviser is a real argument on penalties.
Is every mistake worth correcting?
No, and a good reviewer will say so. A small error in your favour that costs more to fix than it returns is best left, while a missing information return usually is not. The decision turns on exposure rather than on tidiness.
Our guide to amending a US return covers the mechanics.
Amending also reopens the year to questions.
When should you ask for a second opinion?
After a year with anything unusual in it: a move, a house sale, a share exercise, a redundancy or an inheritance. Those are the years where a preparer unfamiliar with Britain is most likely to be out of their depth.
Our guide to UK settlement agreements covers one such year.
Routine years are rarely worth reviewing twice.
What about missing reporting forms?
That is the finding with real money behind it, because information return penalties start high and apply per form per year. Established routes exist for coming forward, and they work far better before anybody writes to you.
Our guide to delinquent information returns covers the catch-up.
The IRS treats a voluntary disclosure very differently from a discovery.
Does a British return need reviewing too?
Often, and for mirror image reasons. A British accountant who does not see the American return can misstate foreign income or miss a claim, and the two returns should tell the same story. Reviewing one without the other is half a job.
Our guide to an HMRC enquiry covers the British process.
Inconsistency between the two invites questions in both.
Can a review find money you never claimed?
Regularly. Refundable credits for children, surplus foreign tax credit that could have been carried back, and British reliefs never claimed all turn up. These are claims rather than corrections, and they have their own time limits.
Our guide to the child tax credit abroad covers one common claim.
Unclaimed is as costly as overstated.
How long does a second opinion take?
A couple of weeks for three years, assuming the documents arrive together. Most of the delay is waiting for transcripts or for British paperwork. The analysis itself is quick once everything is on the table.
Our guide to the IRS online account covers getting records quickly.
Order transcripts the day you commission a review.
What should a second opinion look like?
A short written note listing each finding, what it is worth, and whether to act on it. A verbal reassurance is not a review. You should be able to hand that note to anybody and have them understand the position.
Our guide to the US-UK tax treaty covers a related point.
Ask for it in writing before you commission anything.
Does a second opinion mean changing accountant?
Not at all, and most people do not. A review is a one-off piece of work, and plenty of clients take the findings back to their existing preparer to fix. The point is the return rather than the relationship.
Our guide to IRS letters after streamlined covers correspondence.
A good preparer welcomes a clear list of findings.
What if the return was self-prepared?
Then a review matters more, because the software never asked the right questions. Consumer packages handle the exclusion reasonably and the credit badly, and they rarely mention the reporting forms at all. Self-prepared expat returns are the ones we find most on.
Our guide to US filing thresholds for expats covers who must file.
Cheap software is expensive on a cross-border return.
Can a review cause an audit?
Looking at your own return changes nothing, because nobody outside sees it. Amending a year does draw a little attention to that year, which is one reason a reviewer should tell you when not to amend. The review itself is invisible.
Our guide to an IRS audit from abroad covers examinations.
A quiet file stays quiet while you read it.
Does a second opinion help before you move?
Enormously, and that is the best time to pay for one. A review before a move looks forward rather than back, and the decisions you take in the months before leaving set the tax position for years. Afterwards you are correcting rather than planning.
Our guide to moving back to the US covers leaving Britain.
Advice before a move beats a review after one.
What about share schemes and bonuses?
Those are where the largest errors sit, because an option exercise or a long-term award spans two countries and several years. A preparer who sees only the American side usually takes the figure on the statement and stops there.
Our guide to US-UK share schemes covers the awards.
Ask specifically about any year you exercised something.
Does it cover state returns?
It should, because a lingering state filing is a common and expensive oversight. Somebody who moved abroad from California or New York may still have a state return nobody has looked at. The federal review often misses it entirely.
Our guide to state tax for expats covers the stubborn states.
Ask whether the scope includes the state.
How often should you have one?
Once every few years for a steady position, and after any unusual year. A review every twelve months is rarely worth it where nothing has changed. The events matter more than the calendar.
Our guide to the UK tax year difference covers the recurring work.
Three years is a sensible interval for most people.
What if you have missed years entirely?
That is a different job from a review, though it often starts as one. Where returns were never filed at all, the catch-up procedures apply rather than amendments. A reviewer should spot the difference immediately and say so.
Our guide to streamlined eligibility covers the route back.
Unfiled years and wrong years need different treatment.
Does a review help with a pending notice?
Often decisively, because the notice tells you what the IRS thinks and the review tells you whether it is right. Answering a letter without knowing whether the underlying return was correct is guesswork. Deadlines still govern the reply.
Our guide to a CP2000 notice from abroad covers those letters.
Diarise the reply date before commissioning anything.
Who should not bother?
Somebody with a single British salary, no investments and a preparer who files both returns. That position is hard to get wrong and cheap to check informally. The value rises sharply with the number of moving parts.
Our guide to US tax deadlines for expats covers the routine year.
Simple affairs rarely repay a formal review.
What makes a reviewer qualified?
Filing both returns regularly, rather than knowing one system well. Somebody who has never prepared a Self Assessment cannot tell whether British tax was stated correctly, and the reverse is equally true. Ask directly how many of each they file.
Our guide to an enrolled agent against a CPA covers the credentials.
Credentials matter less than doing both every week.
Can you review your own return?
You can check the arithmetic and the obvious omissions, and you will miss the judgement calls. The errors that cost most are choices between two defensible treatments, which is exactly what an unfamiliar eye is for.
Our guide to Form 8833 treaty positions covers one such choice.
Start by comparing the return against your payslips.
How to get a second opinion
- Gather the last three American returns and the British ones.
- Order your account and wage transcripts at the same time.
- Add payslips, P60s and any notices you received.
- Agree a fixed fee and a defined scope in writing.
- Ask specifically about the exclusion against the credit.
- Ask which reporting forms were due and which were filed.
- Decide which findings are worth correcting.
- Amend the open years before they close.
Mistakes and penalties we see without a second opinion
The first is years of the exclusion where the credit would have been worth more, quietly overpaying and never knowing.
The second is a P60 transcribed straight onto an American return, reporting the wrong twelve months every single year.
The third is a workplace pension reported as a foreign trust, generating forms nobody owed and penalties when they were late.
The fourth is a missing account report discovered by the IRS rather than disclosed, which removes every gentle route back.
How US UK Tax Accountants helps
We read the return against the source documents rather than against itself, because a return can be internally consistent and still report the wrong twelve months.
Then we tell you which findings are worth acting on. Our US federal returns service covers the corrections.
If nobody who files both returns has ever looked at a cross-border year, get in touch.
Last reviewed 29 October 2026. This article is general information and not personal tax advice, and outcomes depend on your facts.
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Official guidance from the IRS, FinCEN and GOV.UK. Thresholds and rates on those pages are updated annually — check the current tax year before relying on a figure.
