UK savings interest, the allowances, and your US return

It is an amount of savings interest you can earn each tax year without paying UK tax on it. HMRC states that you may get up to £1,000 of interest tax-free, and how much you get depends on your income tax band.

It sits alongside two other allowances. Your personal allowance covers income generally, and a separate starting rate for savings can cover interest for people with modest other income.

The GOV.UK guidance on tax-free interest explains how the three interact. They apply for each tax year, which runs from 6 April to 5 April.

It gives up to £5,000 of savings interest at a zero rate, but it shrinks as your other income rises. HMRC reduces it pound for pound by other income above the personal allowance of £12,570.

So someone with a substantial salary usually gets none of it. Someone living mainly on savings, such as a retiree or a person between jobs, can get a great deal of it.

The worked example on GOV.UK shows the taper directly. Other income of £16,000 reduces the starting rate by £3,430, leaving £1,570 of savings interest still covered.

Because the American system has no equivalent. Interest is ordinary income there, reported in full, and no British allowance carries across. So interest that costs you nothing here can cost you something there.

The reporting sits on Schedule B alongside dividends, as IRS Topic 403 describes. Foreign interest belongs on the return in the same way as domestic interest.

This is the reverse of the usual cross-border pattern. Normally British tax exceeds American tax and credits absorb the difference. With savings interest, the British charge is often nil.

Only if you actually paid some. Foreign tax credits work on tax paid, so interest covered by an allowance generates nothing to claim. The American charge then stands on its own.

Where you do pay UK tax on interest, because your allowances are used up, that tax can support a credit through Form 1116 in the right income category.

Our guide to avoiding double taxation covers how the categories work. Interest sits in the passive basket, so credits from salary cannot shelter it.

The account behind it might. Foreign account reporting depends on balances rather than income, so a savings account paying trivial interest can still need disclosing. The two questions run on entirely separate rules, and answering one tells you nothing about the other.

That reporting is separate from the tax and runs on its own thresholds. Our guide to Form 8938 and the FBAR sets out the two regimes and how they differ.

So savings accounts generate two questions, not one. Is the interest taxable, and does the account itself need reporting? The answers are independent.

Yes. Banks and building societies report the interest they pay to HMRC each year, which is why tax codes sometimes change after a good savings year. You do not have to declare it for HMRC to know about it.

That reporting is one reason untaxed interest rarely stays invisible. It is also why a mismatch between your return and the bank data tends to surface on its own.

The American side has its own information flows, including account data that crosses borders each year. So consistency between the two returns matters as much here as anywhere else.

This takes a few minutes once a year, and it prevents the common surprise of American tax on British interest.

Keep the workings with your other records. Interest figures are easy to gather and easy to forget.

Britain ignores it and America does not. A cash ISA pays interest free of UK tax, and that interest stays fully reportable and taxable on an American return. The wrapper removes one country from the picture and leaves the other exactly where it was.

The wrapper is still useful for the British side, and a cash version avoids the fund problems that catch stocks and shares accounts. Our guide to ISAs and the PFIC problem covers that comparison.

In our practice we see people assume the ISA solves both systems. It solves one, and the other never notices it existed.

Materially, yes. When rates were near zero, ordinary savers rarely used their allowances at all. Higher rates push more people past them, which changes the British answer as well as the American one.

It also brings more people into Self Assessment, since untaxed income above certain levels needs reporting here. Our guide to how HMRC knows about your income covers how banks report interest.

So an allowance that covered everything two years ago may not cover everything now. It is worth re-checking in a year when rates or balances have moved.

It works in reverse. Interest from an American bank is foreign income to Britain, so it belongs on your Self Assessment return if you are UK resident and it is taxable here.

American banks may also withhold tax in some circumstances, and where they do, that tax can support a credit against the British charge. Keep the year-end statements that show it.

So an American in Britain can have interest flowing in both directions, each reportable in both systems. The allowances only ever apply to the British side of that picture.

Take an illustrative example: an American teacher in Bristol with a salary and a savings account paying £900 of interest. Her personal savings allowance covers the interest, so she pays no UK tax on it.

Her American return treats that £900 as ordinary income, converted to dollars. Because she paid no British tax on it, she has no credit to claim, and the interest is taxed on the American side alone.

Her neighbour, a British citizen with no American ties, simply enjoys the allowance and files nothing. Same account, same interest, and an entirely different amount of paperwork.

Peer-to-peer lending pays interest, so the personal savings allowance can cover it in Britain in the ordinary way. The American side taxes it as ordinary income, exactly as it taxes bank interest.

Corporate and government bonds pay interest too, though the British treatment of gains on them differs from the treatment of the income. The two elements need separating before either return gets completed.

Fund-held bonds are a different animal again, because the fund itself brings the foreign fund rules with it. What looks like interest to a British investor can be something quite different on an American return.

It can. Where HMRC expects interest above your allowances, it may collect the tax through your PAYE code rather than asking for a payment. That is why a good savings year sometimes shows up in a changed code notice.

Check the figure behind any such change, because it rests on an estimate from earlier data. Estimates go stale when rates or balances move.

The American return sees none of this. It taxes the interest as income regardless of how Britain chooses to collect anything due here.

The first is leaving interest off the American return because no tax was deducted here. Deduction at source is not the test; receipt of the income is.

The second is expecting credits to cover it. Credits follow tax paid, so an allowance that removes the British charge also removes the credit that would have offset the American one.

The third is forgetting joint accounts. Interest on a joint account belongs partly to each holder, and an American holder reports their share whoever else is named.

Annual interest certificates from each bank, plus the monthly statements behind them. The certificate gives the British tax year figure, while the statements let you rebuild calendar-year totals for the American return.

Keep a note of joint account shares as well. Where an account is held jointly, only your share belongs on your return, and the split needs recording rather than remembering.

Ten minutes of filing each year saves an afternoon later. Interest is the easiest income to gather and the easiest to overlook entirely.

We handle interest alongside the rest of both returns through our treaty relief service, including the split between tax years and the account reporting behind it. Where the British allowances leave an American charge, we say so before the bill appears.

If your savings have grown or rates have moved, send us the figures and we will check both sides at a fixed fee agreed first. HMRC's income tax rates page shows the bands the allowances depend on. This article is general information, not personal tax advice; take advice on your own facts from a qualified adviser.