Separating across two tax systems, and the rules that differ

Any separation where both tax systems have a claim on the same settlement. That covers an American couple in Britain, a mixed-nationality couple anywhere, and a British couple holding American assets.

The common thread in a cross-border divorce is that one settlement gets measured twice. Each country applies its own rules to the same transfers, the same home and the same pensions.

So the question is rarely what the divorce itself costs. It is which country taxes which part, and when.

Generously, and more generously than it used to. Where you lived together at some point in a tax year, assets can move between you at no gain or loss until the earlier of the end of the third tax year after you stopped living together, or the date of the divorce order.

Transfers made under a formal divorce or separation agreement, or a court order, are at no gain or loss with no time limit at all. The HMRC helpsheet on separation and divorce sets out both rules.

Those rules apply to disposals from 6 April 2023. Older advice will tell you the window closes far sooner than it now does.

Usually nothing at all, which surprises people expecting a bill. Transfers between spouses, or between former spouses incident to a divorce, generally trigger no gain or loss, and the recipient takes over the cost basis.

That symmetry is the reason most American divorces are not taxable events in themselves. The tax arrives later, on a sale.

So far the two systems broadly agree. The next section is where they stop agreeing.

Because the American nonrecognition rule has an exception that catches exactly this situation. Where the spouse or former spouse receiving the property is a nonresident alien, the usual no gain or loss treatment does not apply.

So in a cross-border divorce, an American transferring an appreciated asset to a British former spouse can realise a taxable gain on the transfer itself. There may be no sale, no cash, and a large dollar gain.

The IRS guidance on a nonresident spouse explains the wider treatment of mixed couples. In our practice this single rule reshapes more settlements than any other.

Not at all, on the American side, for modern agreements. The IRS states that the payer cannot deduct maintenance under a divorce or separation agreement executed after 2018, and the recipient does not include it in income.

Older agreements can still follow the previous rules, where payments were deductible and taxable. A modification can bring an older agreement into the new treatment if it says so expressly.

The IRS page on alimony sets out both regimes. Britain does not tax maintenance as income either, so for once the two systems land in a similar place.

Each country applies its own relief, and the timing of a move matters. Britain gives Private Residence Relief by reference to occupation, while America gives a capped exclusion tied to ownership and use.

In a cross-border divorce, a spouse who moves out early can lose part of the relief in one country while keeping it in the other. Those rules are worth checking before anyone moves out, not afterwards.

Our guide to selling a UK home as a US person covers both calculations, including the currency effect and the mortgage.

Agree who stays and who leaves with both reliefs in view. That single decision often moves more money than the rest of the schedule.

Through orders that each system recognises in its own way, so one order rarely does both jobs. British pension sharing orders divide a pension without an immediate tax charge here.

The American treatment of a British pension share is a separate question, and it depends on the scheme and the treaty position. Our guide to UK pensions under US rules explains the underlying framework.

American retirement accounts split on their own rules, usually through a qualifying court order. Do not assume a British order reaches an American plan.

Where the American rule applies, you take over your former spouse's cost rather than the value on the day. So an asset that looks like a clean settlement can carry a large built-in gain into your own hands.

That matters when you later sell. Two assets of equal value today can produce very different bills, depending on what each one originally cost.

Ask for the original purchase records as part of the settlement. Reconstructing a cost from fifteen years ago is far harder once the relationship has ended.

It depends on where you stand on the last day of the year. Your marital status on 31 December generally decides the status for the whole year, which makes the timing of a final order a tax decision as well as a legal one.

Separated but still married on that date usually means married filing jointly or separately. Our guide to married filing separately with a UK spouse covers the second option and its low threshold.

Some separated parents qualify for head of household, which is more favourable. The conditions are specific, so check them rather than assuming.

Generally the parent the child lived with for most of the year, under the American rules. That parent can release the claim to the other parent using the relevant IRS form.

Credits depend on the child having the right identifying number, which matters for families abroad. The IRS guide to dependents sets out the tests, and our guide to the child tax credit abroad explains the conditions.

British child benefit follows its own rules, and the high income charge can land on whichever parent earns more. The two systems make entirely separate decisions here.

More than almost anything else in a cross-border divorce, and it is the part lawyers can usually accommodate. The British transfer window runs from when you stop living together, while American filing status turns on 31 December.

A settlement finalised in December and one finalised in January can produce different bills from identical facts. Neither outcome is wrong. They are simply different tax years.

So put the tax dates in front of the lawyers early. Most orders can accommodate a sensible timetable if someone asks in time.

Both sides of the paperwork change after a cross-border divorce, and people forget the reporting rather than the tax. Accounts you keep, accounts you close and accounts you receive all affect your foreign account reports.

Our guide to Form 8938 and the FBAR sets out the two regimes. Joint accounts that become single accounts need attention in the year they change.

Update the list in the year of separation rather than the year after. Reconstructing balances for a year you would rather forget is miserable work.

A cross-border divorce also changes who signs what. Where you held authority over an account you no longer own, say so in the year it changed.

It often does, because one person frequently moves country. A change of residence mid-settlement affects which system taxes what, and it can open or close reliefs on both sides at once.

Our guide to the statutory residence test explains when British residence starts and ends. The date matters as much as the destination.

Where a move is planned, sequence it with the order rather than around it. Moving first and settling later produces a different result from the reverse.

Work through this while the settlement is still under negotiation. Almost every item is cheaper to plan than to fix.

Share the list with your solicitor, since several points affect the wording of the order.

Take an illustrative example: an American in Bristol separates from her British husband. The settlement gives him a rental flat she has owned for fifteen years, with a substantial gain.

In Britain the transfer passes at no gain or loss under their court order. On her American return, the nonrecognition rule does not apply, because he is a nonresident alien.

She therefore faces an American gain on a transfer that produced no cash. Spotting it during negotiation let them choose a different asset and avoid the charge.

The first is assuming spousal transfers stay tax-free everywhere. That assumption breaks the moment one spouse is not American.

The second is using old British guidance. The transfer window is considerably longer than it was before April 2023.

The third is treating maintenance as a deduction. For agreements made after 2018 there is nothing to deduct and nothing to declare.

The fourth is leaving the tax questions to the end. By the time an order is drafted, most of the choices have already been made.

We work alongside family solicitors through our treaty relief service, modelling settlements before anyone signs rather than reporting them afterwards. Where one option costs materially less, we show the numbers.

If you are separating and either of you has an American connection, send us the outline and we will map both systems at a fixed fee agreed first. This article is general information, not personal tax or legal advice; take advice on your own facts from qualified advisers.