IHT400 and the inheritance-tax forms

Last reviewed 18 August 2026

The paperwork of inheritance tax alarms more executors than the tax itself. In truth, many estates need very little of it — the trick is knowing which camp yours falls in.

Which form, and when

Where inheritance tax is due, or the estate does not qualify as “excepted”, the full account is made on IHT400 with its schedules. Many estates are excepted — broadly, smaller estates, or those passing entirely to a spouse or charity — and need only the reduced reporting that now runs through the probate application itself. Check the current excepted-estate conditions before assuming which applies.

How it fits with probate

Inheritance tax generally has to be reported (and any tax paid, or arranged) before the grant of probate is issued — the two processes interlock. HMRC now charges interest on inheritance tax paid late (7.75% from 9 January 2026), so the timing matters. For a complex estate, this is the stage at which many executors take advice.

Sources. GOV.UK, Inheritance Tax forms (IHT400 and excepted estates); HMRC interest rate 7.75% from 9 January 2026 — confirm current excepted-estate thresholds at build.