For most Americans paying UK tax, the foreign tax credit beats the deduction, because a credit comes off US tax itself and needs no itemising. The deduction can win in a narrow set of years, typically one where UK tax is paid but the credit limit is nil. The IRS guidance on the choice (opens the official IRS page in a new tab) tells you to work out your tax both ways.
This post is for US citizens and green card holders with UK tax on a return, particularly in a year of change such as a move back to the United States. Our guide to avoiding US-UK double taxation mentions the deduction in passing. Here we look at the years when it deserves a calculation, what the all-or-nothing rule costs, how long you have to change your mind, and a checklist for deciding.
When can deducting UK tax beat the credit
Deducting can win when the credit would save little or nothing this year and has poor prospects in other years. That points to a low or nil limit on foreign-source income, and enough other itemised deductions for Schedule A to beat the standard deduction. Both conditions have to hold together.
The limit comes first. Publication 514 (opens the official IRS page in a new tab) caps the credit at US tax multiplied by a fraction, with foreign-source taxable income on top. Where that income is zero or less for a category, the limit for that category is zero. UK tax can still fall in that year, because the paid method follows the date of payment and not the year the income was earned, as our post on paid or accrued UK tax explains.
The itemising test comes second. A credit can be taken alongside the standard deduction, while a deduction requires Schedule A. The standard deduction for tax year 2025 is $15,750 for a single filer, so UK tax only helps to the extent that it lifts total itemised deductions above that figure. Even then, the deduction saves only the US tax at your top rate on that amount, where a usable credit saves the whole amount.
- Little or no foreign-source income in the category. The limit is small or nil, so the credit has nothing to offset
- UK tax on income that stays US-source. The credit gives no room unless the treaty re-sources that income
- Excess tax with no realistic later use. The carryover would probably lapse, leaving the deduction as the only value
Can you credit some UK tax and deduct the rest
Generally not. For each year you either credit all qualified foreign taxes or deduct all of them, whichever country or income they relate to. You cannot credit the UK tax on your salary and deduct the UK tax on some other item that the credit limit cannot reach.
This rule decides most cases of US-source income. Publication 514 sources wages by where the work is done, so UK tax on pay for days worked in Boston has no foreign-source income behind it under domestic law. A deduction looks attractive for that slice, yet taking it means deducting the UK tax on every other pound of salary as well. Test re-sourcing under Article 24 first, because the treaty may bring the income within the credit. Our treaty relief service works through that item by item.
The exceptions are narrow. The Form 1116 instructions (opens the official IRS page in a new tab) and Publication 514 allow a deduction alongside a credit for certain taxes that are denied a credit, including those caught by the boycott rules or by the holding period rules on withholding tax. Our post on which UK taxes count deals with charges outside the system altogether. National Insurance gets neither a credit nor a deduction, and foreign property taxes on a personal home cannot go on Schedule A.
What does a deduction year do to carryovers
It blocks them and can burn them. You cannot credit a carryover in a year when you deduct, and if that year would have had excess limit, Publication 514 treats carryovers as absorbed up to that excess, with no benefit. Where the limit is nil, there is no excess, so nothing should be absorbed.
To run the test, compute the limit as though you had chosen the credit, even though you are deducting. Any amount by which that limit exceeds the year's own foreign tax in the category eats the oldest carryover in that category. A person holding a large pool in a year with real foreign income can therefore lose part of it for nothing, which is often the deciding cost.
Those absorbed taxes can be recovered only by changing the deduction year to a credit. The opposite case is the one where deducting is cleanest: no foreign-source income in the category means no excess limit, so the pool passes through untouched. Our post on carrying excess UK tax credits covers how the pool itself is used and tracked.
Can you deduct a credit that is about to expire
No. Publication 514 says unused foreign taxes cannot be deducted in any year to which they are carried. The only way to deduct them is to change the year they arose from a credit to a deduction, and that window usually closes long before the carryover runs out.
Set the two clocks side by side. A carryover runs back one year and forward ten. Publication 514 gives you three years from filing or two years from payment, whichever is later to switch a year from credit to deduction. By the time a balance is close to expiry, its original year has normally been closed to that switch for years. The decision about a doubtful carryover therefore belongs near the start of its life.
The switch is also expensive. Changing the original year on Form 1040-X means deducting all of that year's foreign tax, including whatever the credit had already used. Where the credit wiped out the US tax on a full UK salary, a deduction would rarely match it. It is worth modelling mainly for a year in which most of the UK tax went unused, such as a year with little foreign-source income.
How does the choice work for someone moving home
Take a US citizen who worked in Manchester, moved to Denver and uses the paid method. A Self Assessment balance for her last UK tax year falls due in a calendar year when she works every day in Denver. She has one payment to HMRC, no foreign income and a nil limit.
The payment is due by 31 January. With the credit, it saves nothing in the year it is paid. It can be carried back to the previous year only if that year's general category has excess limit, and her UK salary had filled that limit. Carried forward, it needs foreign-source earnings that bear less foreign tax than the US tax on them. She has no plans to work abroad, so the carryover looks unlikely to be used.
With the deduction, the payment goes on Schedule A, line 6 (opens the official IRS page in a new tab). The instructions apply the state and local tax limit to lines 5a to 5c, and foreign income taxes sit outside those lines. Her mortgage interest and state tax already bring her near the $15,750 standard deduction, so most of the payment produces a real saving at her top rate. Her old carryover is untouched, because a nil limit leaves no excess. On these facts the deduction may win, and Form 1040 should be computed both ways to confirm it.
Change one fact and the answer can move. If she spends five working days in Paris that year, those days are foreign-source earnings and the limit is no longer nil. The credit now has some value, and a deduction would forfeit it. Had she elected the accrual method earlier, the payment would not arise in this year at all: the IRS page (opens the official IRS page in a new tab) says accrued taxes paid later cannot be deducted.
How do you change the choice for an earlier year
You amend. Publication 514 gives ten years from the regular due date of the return, ignoring extensions, for the year the tax was paid or accrued to move from a deduction to a credit. Moving from a credit to a deduction has a much shorter period, and either can be extended by agreement.
The time limits are uneven for a reason worth using. A Form 1040-X (opens the official IRS page in a new tab) moving from credit to deduction must meet the three years from filing or two years from payment, whichever is later test. A deduction can therefore be chosen in a doubtful year with a long period to reverse it if foreign-source income later appears. The Form 1116 instructions treat a change from a deduction to a credit as a foreign tax redetermination, so the revised Form 1116 has to follow those rules.
One further point applies to higher earners. The Form 8960 instructions (opens the official IRS page in a new tab) let foreign income taxes attributable to net investment income be entered on line 9b, but not where a credit was taken for any portion of them. The 3.8% tax is generally not creditable under domestic law, and treaty-based claims are contested. So a deduction may reduce it in a way the credit does not, and that belongs in the comparison. Our individual tax returns and cross-border tax services run both versions, alongside the wider reliefs in the double taxation guide.
- Find the foreign-source income in each category for the year. If it is nil, the deduction deserves a calculation
- Check the UK tax for income that could be re-sourced under the treaty before treating it as stranded
- List itemised deductions without the UK tax, and see how far they fall short of the standard deduction
- Compute the limit as if crediting, and note any excess limit that would absorb a carryover
- Estimate realistically whether foreign-source income will arise within the carryover period
- Compute total US tax both ways, including net investment income tax, and keep both workings
General information, not advice. The right answer depends on your circumstances and the tax year concerned.
