IHT Deemed Domicile: The 15-Year Rule and Spouse Election
A non-UK domiciled person who has been UK resident for 15 of the past 20 tax years is treated as UK domiciled for IHT — all their worldwide assets fall into the UK IHT net. Non-dom spouses can elect for deemed domicile to gain unlimited IHT spouse exemption.
Three Routes to Deemed UK Domicile for IHT
3-year rule — s267(1)(a)
When it applies: Was UK domiciled under general law within 3 years before the transfer
Effect: Treated as UK domiciled for that transfer — worldwide assets in scope
15-year rule — s267(1)(b)
When it applies: UK resident in 15+ of the 20 tax years ending with the transfer year
Effect: Treated as UK domiciled for IHT — worldwide assets in scope
Formerly domiciled resident (FDR)
When it applies: Born in UK with UK domicile of origin; now UK resident again
Effect: Immediately treated as UK domiciled for each tax year of UK residence (no waiting period)
Non-dom spouse election — ss267ZA-267ZB
When it applies: Non-dom spouse/civil partner of a UK domiciled (or deemed UK domiciled) person makes a written election to HMRC
Effect: Unlimited IHT spouse exemption (removes the £325,000 cap on transfers to non-dom spouse)
Frequently Asked Questions
What is deemed domicile for IHT purposes?
A person who is not UK domiciled under general law can still be treated as UK domiciled for Inheritance Tax purposes under two rules in s267 IHTA 1984: (1) The 3-year rule (s267(1)(a)): a person who was UK domiciled under general law within the 3 years before a chargeable transfer (or death) is treated as UK domiciled for that transfer. This catches people who have recently left the UK; (2) The 15-year rule (s267(1)(b)): a person who was resident in the UK for at least 15 of the 20 tax years ending with the tax year in which the transfer (or death) occurs is treated as UK domiciled for IHT. The 15-year rule was introduced in the current form by the Finance (No. 2) Act 2017 (replacing a 17-year rule). Once deemed domicile applies, the person's worldwide assets are within the scope of UK IHT — not just UK-sited assets.
How does the 15-year deemed domicile rule work in practice?
The 15-year rule counts tax years (6 April to 5 April) of UK residence immediately preceding the tax year in which the transfer or death occurs. Partial years of residence count as a full year of residence for this purpose. Example: a person leaves their country of birth in 2005 and becomes UK resident. By 2026 they have been UK resident for 21 tax years. They became deemed UK domiciled for IHT after their 15th year of UK residence — so their entire worldwide estate has been within UK IHT since then. To lose deemed domicile, a person must be non-UK resident for more than 5 consecutive tax years (6 tax years in total breaks the chain). The 3-year shadow rule means that even after ceasing to be deemed domiciled, they remain treated as UK domiciled for 3 further years.
What is a 'formerly domiciled resident' for IHT?
A formerly domiciled resident (FDR) is a person who was born in the UK with a UK domicile of origin, who then acquired a non-UK domicile of choice, but who subsequently returned to UK residence. Since 6 April 2017, FDRs are treated as UK domiciled for income tax, CGT, and IHT purposes for any tax year in which they are UK resident. This prevents a person born in the UK from avoiding UK taxes by acquiring a foreign domicile and then returning to live in the UK. Unlike the 15-year rule, the FDR rule applies immediately on resuming UK residence — there is no 15-year waiting period. The rule applies if: (1) the person was born in the UK; (2) their domicile of origin is UK; (3) they were resident in the UK in the relevant tax year.
Can a non-UK domiciled spouse elect to be treated as UK domiciled for IHT?
Yes — under ss267ZA-267ZB IHTA 1984, a non-UK domiciled spouse or civil partner of a UK domiciled (or deemed UK domiciled) person can elect to be treated as UK domiciled for IHT purposes. The effect of the election is to give the couple unlimited IHT spouse exemption — removing the £325,000 cap that applies to transfers between a UK domiciled and a non-UK domiciled spouse. Without the election, transfers from a UK domiciled spouse to a non-UK domiciled spouse are only exempt up to the non-domiciled spouse's available nil-rate band (£325,000 as at 2026). The election is made in writing to HMRC and takes effect from the date of the election. It is irrevocable during the UK domiciled spouse's lifetime, but can be revoked within 2 years of the UK domiciled spouse's death if the non-dom spouse then leaves the UK.
How can deemed domicile be avoided or lost?
The 15-year rule is lost by being non-UK resident for 6 or more consecutive tax years. Once this is achieved, the person is no longer deemed domiciled under the 15-year rule — but the 3-year rule may still apply if they were UK domiciled in general law within the last 3 years. Planning for non-doms who want to avoid deemed domicile: (1) Leave the UK before accumulating 15 years of UK residence; (2) Place non-UK assets into an excluded property trust before becoming deemed domiciled — excluded property trusts created while not deemed domiciled can hold non-UK assets outside UK IHT even after deemed domicile is acquired; (3) After leaving the UK, ensure you do not trigger the 3-year shadow (avoid UK-domicile-like connections for 3 years). FDRs cannot avoid deemed domicile while remaining UK resident — the FDR rule applies immediately and indefinitely for each tax year of residence.
UK Estate Planning for Non-UK Domiciliaries
If you are approaching deemed domicile, or your spouse is non-dom, estate planning must be done before the 15-year threshold is reached. A will is the foundation. WillSafe kit from £19.97.