The standard nil-rate band is £325,000; a residence nil-rate band of up to £175,000 can apply where a main home passes to direct descendants, tapering away for estates above £2m. Transfers between UK-domiciled spouses are exempt, and unused bands are transferable between spouses.
UK real estate is "situated" in the UK for IHT, so a non-domiciled, non-resident owner's UK house or flat is still taxable on death — a point many international buyers miss when they hold property personally. Since April 2017 UK residential property held through an offshore company or partnership is also looked through for IHT, closing the old "envelope" planning.
Structuring (trusts, debt, life cover, spousal routing) can materially change the exposure, but the rules are anti-avoidance-heavy and change often. Any structure should be set up with specialist advice before purchase — unwinding one later triggers SDLT and CGT.