More non-doms left Britain after the 2017 reform. The Treasury still made over £1bn more.
HMRC's own evaluation: after the 2017 non-dom reform, affected taxpayers were 10-12% more likely to leave the UK than normal. The Treasury still raised over £1bn more per year from those who stayed. People leaving doesn't automatically mean a policy loses money.
The claim
If you tax wealthy people more, they leave, and the country loses money.
What is true
More people really did leave: HMRC's own evaluation found affected long-term non-doms were 10-12% more likely to leave the UK than normal, against a 4-5% baseline departure rate — a real, measured increase, not a rounding error.
Put it in scale
10-12%
More likely to leave (vs. normal churn)
HMRC's own difference-in-differences estimate, against a 4-5% "normal churn" baseline in an unaffected comparison group — a robustness check elsewhere in the same evaluation widens this to a 4-11 percentage-point range.
£1bn+
Extra tax raised from stayers, TY2020
Up from over £700m in the tax year ending 2018.
What we know / don’t know
How much of the extra revenue reflects stayers genuinely earning/declaring more, versus other taxpayers shifting income to avoid a different rule?
HMRC's own evaluation states its £3bn+/year stayer-contribution figure and its revenue-increase figures are LOWER-BOUND estimates, built from a difference-in-differences design that excludes some non-domiciled sub-groups from the regression sample — it does not attempt to fully decompose the mechanism behind the increase.
The verdict
Both are true: departures rose because of the reform, and the Treasury still ended up with over £1bn more per year from those who stayed.
Every number on this card
| Figure | What it counts | Geography · period | Status | Source |
|---|---|---|---|---|
| 10-12% | Affected long-term non-doms more likely to leave the UK, due to the 2017 reformHMRC's own difference-in-differences estimate, against a 4-5% "normal churn" baseline in an unaffected comparison group — a robustness check elsewhere in the same evaluation widens this to a 4-11 percentage-point range. | United Kingdom · Tax years ending 2015 to 2018, vs. a control group | MODELLED | HMRC, "Evaluation of the change to UK Deemed domicile policy 2017" |
| £1bn+ | Additional UK tax raised from those who remained, tax year ending 2020, vs. their pre-reform baselineUp from over £700m in the tax year ending 2018. | United Kingdom · Tax year ending 2020, vs. tax year ending 2015 | CALCULATED | HMRC, "Evaluation of the change to UK Deemed domicile policy 2017" |
| 9,800+ | Affected taxpayers who remained in the UK after becoming "deemed domiciled"HMRC's own broader estimate, including taxpayers who don't proactively declare deemed-domicile status, puts this as high as 15,600 — contributing over £3bn/year in Income Tax, CGT and NICs, which HMRC itself calls a lower-bound estimate. | United Kingdom · As at the tax year ending 2020 | KNOWN | HMRC, "Evaluation of the change to UK Deemed domicile policy 2017" |
- This is Britain's own single most direct "natural experiment" on taxing a mobile wealthy population more — it does not by itself prove any future, different tax change would have the same result.
- A closely related academic estimate (that stayers paid "155% more" and emigrants' tax fell "60%") traces to Advani, Burgherr & Summers's 2024 conference slides, cited by HMRC's evaluation — the same team's later 2025 working-paper draft reports different figures (50%/73%) for a related but non-identical specification. See /inequality/millionaire-migration for the full detail.
Verified against primary sources: 2026-09-06.