Moving from the UK does not put US estimated tax on hold. A filing extension may give you more time to send a return, but it does not automatically move the dates for paying enough US tax during the year.
This guide is for US citizens and resident aliens leaving the UK for the United States or another country. It is about federal estimated tax payments for 2026; your UK departure return, destination-country tax and any US state position need their own review.
1. Test whether US estimated tax applies after leaving the UK
Estimated tax is the IRS system for paying tax on income that is not adequately covered by withholding. That can include self-employment profit, interest, dividends, rent, a bonus, a share sale or income from a new overseas role.
For 2026, the general rule is that estimated payments may be needed when you expect to owe at least $1,000 after withholding and refundable credits, and those amounts are below the required safe-payment measure. The IRS describes that measure as the smaller of 90% of the tax on the 2026 return or 100% of the tax on a full-year 2025 return. Higher-income taxpayers and some other cases have different rules, so do not turn that shorthand into a payment instruction without checking Form 1040-ES.
Start with the US estimated tax payments calculator. Enter the income you expect after the move, federal withholding already taken, estimated credits and payments already made. It is a planning screen, not a completed Form 1040-ES or a penalty calculation; use the IRS worksheet and current instructions before you send money.
Gather the inputs before you run a projection
- Your final 2025 federal return, including total tax and adjusted gross income.
- 2026 income records and forecasts, including bonuses, share awards, self-employment and investments.
- Federal withholding and estimated payments already made.
- Expected UK tax and destination-country tax, separated by income category.
- Exact dates you leave the UK, begin work elsewhere and spend time in the United States.
- Prior-year foreign tax credit carryovers and FEIE elections.
A UK tax payment may matter to a later foreign-tax-credit calculation, but it is not US federal withholding.
2. Put the 2026 estimated-tax dates in your move plan
For a calendar-year individual, the 2026 Form 1040-ES payment dates are 15 April, 15 June, 15 September and 15 January 2027. Paying the full expected amount earlier is possible, but a late or too-small payment can still create an underpayment issue.
Use the US expat tax calendar after you have your move date and income timeline. Put each federal date beside the dates your UK salary ends, overseas work starts, equity vests or a property payment arrives. The calendar is an organiser: it cannot decide whether a particular payment is due, whether a disaster extension applies or how a state handles estimated tax.
If income arrives unevenly, the 2026 Form 1040-ES instructions point to the annualized income instalment method where a large change occurs after the first payment period. Keep the date, gross amount, withholding and country-of-work evidence for a relocation bonus, sale, dividend or late-year business profit.
3. Do not confuse an overseas filing extension with payments
US citizens and resident aliens who are living and working overseas on the normal due date can generally receive an automatic two-month extension to file, provided they attach the required statement. For the 2025 calendar-year return, the IRS says the overseas filing date is generally 15 June 2026; Form 4868 is needed only if more time to file is required.
That is a filing rule, not a blanket waiver of tax due or a replacement for 2026 estimated payments. Treat the 2025 return and the 2026 instalment calendar as two separate tracks. If you are unsure whether you qualify as living and working overseas on the relevant date, or how interest and an extension affect your facts, check the IRS guidance or obtain advice before relying on it.
4. Recalculate when foreign tax relief changes the estimate
Leaving the UK can change the foreign tax you expect to pay, the income you expect to exclude and the timing of both. That means an estimated payment based on a January forecast can become wrong by the time you begin work in a new country.
Use the FEIE and Foreign Tax Credit estimator once you have projected foreign earned income, foreign tax and travel days. Use the same assumptions in the estimated-tax calculator; a comparison that uses an optimistic FEIE assumption in one place and a cautious foreign-tax estimate in another is not useful. The tool helps make assumptions visible, but it does not establish eligibility for Form 2555, calculate Form 1116 or decide treaty treatment.
For example, Morgan leaves London in July, receives a UK bonus in August and starts a new overseas role in September. Morgan records the work location and expected foreign tax for each income stream, runs a cautious federal estimate, and updates it when the facts become clearer rather than assuming a future foreign tax credit removes the need for a September payment.
If you are moving to a US state, or retain links to a former state, run the US state tax nexus checker separately. It helps organise connection facts and possible financial exposure; it does not determine state domicile or replace state-specific advice.
5. Keep a payment file that can survive the move
Save the confirmation for every payment with the calculation, payment date, tax year and payment period. A move can make a missing confirmation much harder to recover later.
Also keep final UK pay records, overseas employment documents, the travel calendar, foreign-tax evidence and copies of prior US returns. They support different questions about income timing, work location, foreign tax and payments.
When to get professional advice
Get cross-border tax advice before changing the payment plan if you have self-employment income, stock compensation, a large sale, UK rental income, a pension distribution, a business, a state-residence question or an uncertain FEIE or foreign-tax-credit position. Ask for advice before an instalment date when the income is large or one country’s tax will arrive much later than the US payment date.
Guidance, not advice: the calculators can organise assumptions and comparisons. They do not calculate a final US, UK, destination-country or state tax liability, and they do not replace a tax professional's review of your facts.
A clean payment order after leaving the UK
- Build a 2026 income timeline with withholding, foreign tax and work-location evidence for each significant payment.
- Run the US estimated tax payments calculator using cautious, consistent assumptions and compare it with the current Form 1040-ES worksheet.
- Add the 2026 payment dates to the US expat tax calendar, separately from any filing-extension date.
- Re-run the estimate after a bonus, equity event, new job, foreign-tax assessment or major investment transaction.
- Keep payment confirmations and source records together, then obtain advice before relying on foreign tax relief or a state-residence conclusion for a material amount.
The useful result is not a guessed quarterly amount. It is a dated payment plan that can be updated when the move, income and foreign-tax facts change.