Sterling mortgages and currency gains

Why can repaying a sterling mortgage create a US gain?

Because the US measures everything in dollars. The loan is worth a dollar amount on the day it is taken out and costs a dollar amount on the day each part is repaid. If the pound has fallen in between, repayment costs fewer dollars than the debt was worth, and that saving is treated as income.

The starting rule is in IRS guidance on foreign currency and exchange rates (opens the official IRS page in a new tab): the dollar is the functional currency for individuals, and amounts in another currency are translated into dollars at the rate prevailing when they are received or paid. Publication 54 (opens the official IRS page in a new tab) repeats that every figure on a US return must be expressed in dollars. A sterling mortgage is a debt in a foreign currency, so its dollar value moves with the exchange rate even though the balance in pounds only goes down.

Courts have treated this as taxable. In Quijano v. United States, a 1996 decision of the First Circuit about American taxpayers who bought a house in Britain with a sterling mortgage, the court described an earlier case in which a taxpayer settled a pound debt with cheaper pounds after sterling fell and was held to have a taxable gain. The size of the gain depends on the principal repaid and the rates on the borrowing and repayment dates.

Does section 988 apply to a mortgage on your own home?

Generally not. Section 988 sets the rules for foreign currency gains on debts, but subsection (e) says those rules do not apply to a personal transaction entered into by an individual. A loan on the home you live in is personal, so the gain is taxed under older general principles instead.

The wording matters. Section 988 treats becoming the obligor under a debt in a foreign currency as a section 988 transaction and, in general, treats the resulting currency gain or loss as ordinary income or loss. Subsection (e)(3) then defines a personal transaction as any transaction of an individual, except to the extent that expenses allocable to it are deductible business or investment expenses under sections 162 or 212. Mortgage costs on a home you occupy do not fit that exception.

Congress anticipated this case. The conference report on the 1986 Act, quoted by the court in Quijano, said the section 988 rules would not apply to currency gain or loss recognised by a US individual living abroad on repaying a foreign currency mortgage on a principal residence, and that existing law would continue to govern. Because the section does not apply, its rule on the character of the gain does not apply either, and how the gain is characterised is a point to settle on the facts rather than assume.

Can a currency loss on a UK mortgage be deducted?

Usually not. An individual can deduct a loss only if it arises in a trade or business, in a transaction entered into for profit, or in limited cases from a casualty or theft. A mortgage on your own home is none of these, so a currency loss on repaying it is a personal loss with no deduction.

This is the rule in section 165(c), and Quijano applied it directly. The taxpayers there had a dollar gain on their London house and a currency loss on the sterling mortgage, and asked to set one against the other. The court held that borrowing and repaying the loan was a separate transaction from buying and selling the house, that the loan was neither a business nor a profit-seeking transaction, and that the loss could not be deducted or netted against the gain.

The result is lopsided. When sterling falls, the mortgage produces taxable income. When sterling rises, the mortgage produces a loss the return ignores, and the house itself is more likely to show a larger dollar gain. Over a long mortgage the rate can move both ways, so a borrower can be taxed on gains in some years and get nothing for losses in others.

• Pound falls before repayment. Currency gain on the debt, reportable on the US return
• Pound rises before repayment. Currency loss on the debt, generally not deductible
• Loss on the loan. Cannot be set against a gain on selling the house
• Let property. A loan financing a rental may be treated differently under section 988

Which mortgage events can trigger a currency gain?

Any payment of principal. The gain arises when the debt is paid off, not when the house is sold, so ordinary monthly repayments, lump-sum overpayments, a remortgage that clears the old loan and final redemption can each settle part of the debt at a rate different from the rate when it was borrowed.

In practice the larger events matter most. Monthly repayments reduce principal slowly, and the gain or loss on each is usually small, though it still has to be considered. An overpayment repays a block of principal in one go. Remortgaging with a new lender normally redeems the old loan in full, which settles the whole remaining balance at the exchange rate on that day, even though no money changes hands with the borrower and the new loan starts a fresh calculation from its own date.

A product switch with the same lender may or may not discharge the old debt, depending on the documents, so the offer and completion statement are worth keeping. Each repayment is translated at the rate on the day it is made, following the IRS guidance on exchange rates (opens the official IRS page in a new tab), and the borrowing rate is the one on the day the loan was drawn.

• Mortgage offer and completion statement showing the date and amount drawn
• Annual statements showing principal repaid during each US tax year
• Dates and amounts of any overpayments
• Redemption statements on a remortgage or sale
• The dollar exchange rate for each of those dates

How does the mortgage gain interact with selling the home?

The two are calculated separately. The sale produces a gain or loss on the house, which may be sheltered by the US main-home exclusion. Repaying the mortgage from the proceeds produces its own currency result, which sits outside that exclusion because it does not come from selling the property.

The US exclusion under section 121, described in the IRS topic on the sale of your home (opens the official IRS page in a new tab), applies to gain from the sale of a main home that meets its ownership and use tests, up to a capped amount. Quijano and the IRS position it relied on treat the mortgage as a separate transaction, so the exclusion covers the house and not the debt. Our post on selling a UK home as a US citizen works through the sale itself.

The two often pull in opposite directions. If the pound has fallen since purchase, the dollar gain on the house shrinks, perhaps to nothing, while the mortgage repaid from the proceeds shows a currency gain. If the pound has risen, the house shows a larger dollar gain and the mortgage shows a loss that cannot be used. A seller who plans the timing of a sale or a redemption has to look at both together, which is part of our cross-border property work.

Does the UK tax the gain, and is there a UK credit to claim?

No to both, in the usual case. A UK resident borrows and repays in pounds, so in sterling terms there is nothing to tax, and HMRC treats a loan as a liability of the borrower rather than an asset. With no UK tax on the gain, there is no UK tax for the US to credit.

HMRC's Capital Gains Manual says that, from the borrower's side, a loan is a liability and not an asset, and that foreign currency, meaning currency other than sterling, is the chargeable asset. A sterling mortgage repaid in sterling involves neither. UK private residence relief (opens the official GOV.UK page in a new tab) on the house is a separate matter and has no bearing on the loan.

The foreign tax credit (opens the official IRS page in a new tab) relieves foreign income tax actually paid or accrued, and the treaty's relief article works the same way, so a gain the UK does not tax has no foreign tax of its own behind it. Whether surplus credit for UK tax on other income, carried back one year and forward ten on Form 1116, can absorb the US tax depends on how the gain is sourced and categorised for the credit limitation, and should be checked rather than assumed.

What does this look like for a US citizen with a UK mortgage?

Take a US citizen employed in Leeds who bought a family home with a sterling repayment mortgage, overpaid one year and later remortgaged to a new lender. Each of those repayments of principal is measured in dollars against the rate when the loan was drawn, and the remortgage settles the whole old balance at once.

If sterling was weaker on the remortgage date than on the original completion date, the old loan was cleared with pounds worth fewer dollars than the pounds borrowed, and the difference is a currency gain for that US tax year, reported on Form 1040. The UK return shows nothing. In a year when sterling was stronger, the overpayment would instead show a currency loss that brings no deduction. The new loan begins its own calculation from the new completion date.

The practical steps are to keep the mortgage paperwork, record the rate on each date that matters, and look at the currency position before an overpayment, a remortgage or a sale rather than after. Where a gain was missed in an earlier year, Form 1040-X is the usual route to correct it. We prepare these calculations as part of US returns for Americans in the UK, and the guide to avoiding US-UK double taxation shows where the mortgage fits among the other gaps between the two systems.