What are the main money questions when moving from the US to the UK?

The ones people meet most often are: what happens to US retirement accounts like a 401(k), how the UK decides whether you are tax-resident and when your UK tax year starts, how equity like RSUs that vests after the move is divided between the two countries, and why buying an ordinary non-US index fund can trigger a harsh US regime. Each has its own explainer in this guide. (Source: Two Shores Field Guide overview; individual topics cite their own sources (US–UK Income Tax Convention 2001; Finance Act 2013 Schedule 45; IRC §§1291–1298).)

Does the US stop taxing me once I live in the UK?

No. The US taxes its citizens and green card holders on worldwide income wherever they live, so US rules follow you to the UK, and the UK's own rules apply once you are resident there. Living under both systems at once is the whole reason these questions are tricky, and the US–UK treaty is what coordinates them. (Source: US–UK Income Tax Convention (2001); IRC worldwide-taxation basis for US persons.)

Field Guide

Moving From the US to the UK: The Money Questions, in Plain Language

Rules as of 2026-07-04

Field Guide · Two Shores · twoshores.app

Educational information, not tax or investment advice. Rules described as of the 2026 tax year; always confirm current law or consult a professional for your situation.

You have a move date, or a firm plan to have one. You also have a US financial life: maybe a 401(k) and a Roth, some RSUs that vest on a schedule, a brokerage account, and a habit of buying low-cost index funds. Almost none of that translates cleanly across the Atlantic, and the failures are quiet: nothing in the UK will warn you, because most of what bites is US rules following you, or UK rules you have never met.

This is a map, not the territory. Each question below has a fuller explainer, and the interactive versions live in the US to UK Move Playbook.

What happens to my US retirement accounts?

Your 401(k), IRA, and Roth do not vanish when you leave. How the two countries tax them, and one well-known contested question about the UK tax-free lump sum, are governed by the US–UK treaty. See What happens to your 401(k) and pensions when you move to the UK.

Am I UK tax-resident, and when does my UK year start?

The UK decides residence with the Statutory Residence Test, which counts days and "ties" rather than asking your intentions, and the year you arrive may be split. See How the UK decides if you are tax-resident, and try the free residence day counter.

How are my RSUs split between the US and the UK?

Equity granted before the move but vesting after it is generally divided between the two countries by how much of the vesting period fell on each side. See What happens to RSUs that vest after you move to the UK.

Can I keep buying index funds?

This is the one that surprises people most: for a US taxpayer, an ordinary non-US index fund, even inside an ISA, opts you into one of the harshest corners of the US tax code. See The PFIC Trap, and try the free fund (PFIC) checker.

Two Shores models exactly these questions on your own timeline, with a citation behind every finding. See the US to UK Move Playbook →

Common questions

What are the main money questions when moving from the US to the UK?: The ones people meet most often are: what happens to US retirement accounts like a 401(k), how the UK decides whether you are tax-resident and when your UK tax year starts, how equity like RSUs that vests after the move is divided between the two countries, and why buying an ordinary non-US index fund can trigger a harsh US regime. Each has its own explainer in this guide.Source: Two Shores Field Guide overview; individual topics cite their own sources (US–UK Income Tax Convention 2001; Finance Act 2013 Schedule 45; IRC §§1291–1298)
Does the US stop taxing me once I live in the UK?: No. The US taxes its citizens and green card holders on worldwide income wherever they live, so US rules follow you to the UK, and the UK's own rules apply once you are resident there. Living under both systems at once is the whole reason these questions are tricky, and the US–UK treaty is what coordinates them.Source: US–UK Income Tax Convention (2001); IRC worldwide-taxation basis for US persons