IHT100d is the HMRC form trustees use to report the principal charge, the Inheritance Tax due on each 10 year anniversary of a relevant property trust. It covers the assets that are relevant property immediately before the anniversary. The rate comes from a set calculation on the form, and the tax is due 6 months after the end of the month of the anniversary.
This guide follows the current IHT100d and HMRC's How to fill in form IHT100d, as of October 2026. The IHT100 overview covers the other trust events.
What the anniversary charge is for
The charge falls on each 10 year anniversary, counted from the date the trust started, which HMRC defines as the date assets were first put into the trust. You give that date in Section C, about the trust.
The calculation, box by box
Section H turns the trust's position into a rate. The form's own steps are:
| Box | What you do |
|---|---|
| H1 to H4 | Enter relevant property (F11), related trusts (G2), same-day additions (G6) and historic value of relevant property in other trusts (G7) |
| H5 | Add them up |
| H6 and H7 | Take off the nil rate band available (G19) |
| H8 | Multiply the balance by 20% |
| H9 | Divide by H5 and multiply by 100: the effective rate |
| H10 | Multiply H9 by 30% |
| H11 to H13 | Apply H10 to the relevant property, split into non-instalment and instalment tax |
In other words, the notional pot is charged at 20% above the nil rate band to find an effective rate, and only 30% of that rate is charged on the trust's relevant property. If the nil rate band in G16 is more than the chargeable value in F11, there's no tax and you go to Section J and the declaration.
Section G: the history that sets the band
The nil rate band available isn't simply today's threshold. Section G asks for related trusts made by the settlor on the same day, valued at the trust's start; same-day additions to another trust that increased its value by more than £5,000, as of October 2026; exit charges in the 10 years ending on the anniversary; and the settlor's chargeable transfers, with box G14 looking at the 7 years ending immediately before each one.
HMRC's guide gives a rule for exits. In box G9 you leave out parts eligible for relief, so assets worth £100,000 that left with 50% Business Relief go in as £50,000. A chargeable transfer counts if it increased the value of the trust, whether or not anything went into the trust itself.
Excluded property that becomes relevant property also counts as a chargeable transfer. That happens when a settlor who wasn't UK domiciled before 6 April 2025, or isn't a long-term UK resident after it, becomes a long-term UK resident.
Assets that joined during the decade
The rate is reduced for property that hasn't been relevant property for the full 10 years. The decade is split into 40 quarters, so property that's been in for 5 years, or 20 quarters, pays half the rate from box H10. You list each asset on its own line in boxes H15 and H16, and HMRC's quarters calculator gives the count.
Reliefs from April 2026
From 6 April 2026, 100% Agricultural and Business Relief on the combined value of qualifying property is capped by relief allowances, with value above the allowance relieved at 50%. For the first 10 year anniversary on or after that date, previously relievable property that was in the trust before 6 April 2026 is treated as if it only joined on 6 April 2026. HMRC points to IHTM25551 for detail, and to the D37 and D38 notes for Agricultural and Business Relief. Those are the trust versions of the schedules executors use on a death, where the IHT400 Notes list IHT413 for business and partnership interests and IHT414 for Agricultural Relief.
Box H18 holds a cap on relevant property charges, but only for trusts that held excluded property at 30 October 2024.
Valuing the assets
Section E works the same way as the other event forms: open market value at the anniversary, rounded down to the nearest pound, one total per box, with D schedules for shares, land, insurance, foreign assets and reliefs. Column B covers assets where tax can be paid in instalments over 10 years. Don't include the same asset twice.
Paying, repayments and signing
Tax is due no later than 6 months after the end of the month in which the anniversary fell, and late tax carries interest at a daily rate. You complete the summary table in box H19 using HMRC's interest calculator. Section I gives the account for any repayment, which HMRC makes by Faster Payments to an account in the names of all the signatories. Section J asks for any tax avoidance scheme reference.
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All trustees must agree the declaration. HMRC accepts IHT100 forms without a wet signature as long as every trustee's details are on the declaration page, and an agent adds HMRC's set confirmation statement in Additional information.
Documents: keep them, don't send them
HMRC's guide says to complete every field, because missing information can stop it dealing with the form. You don't send copies of documents such as bank balance letters or evidence of debts unless HMRC asks, but you must keep everything you used, since it may ask later. If you're filling the form in without a solicitor or accountant and want someone else to take HMRC's phone calls, include a separate written authority.
The verdict
The IHT100d isn't hard once you see its logic: build a notional pot from the trust and the settlor's history, find its effective rate, and charge 30% of it. The work is in the history, so keep the original trust values, same-day trusts and every exit since the last anniversary on file, and check the 2026 relief changes before the first anniversary after 6 April 2026.
One more form that confuses people is covered in the trust exit charge return guide.
Frequently asked questions
Do I send bank letters with the IHT100d?
No. HMRC's guide says don't send copies of documents unless it asks, but keep everything you used to fill in the form.
Is there an IHT100d if the nil rate band covers the trust?
You still complete it, but if the nil rate band is more than the chargeable value, there's no tax and you go to the declaration.
What is IHT100d?
The HMRC form for reporting the principal charge on a relevant property trust's 10 year anniversary.
How is the 10 year charge on a trust worked out?
On the IHT100d you find an effective rate by charging the notional pot at 20% after the nil rate band, then take 30% of that rate and apply it to the relevant property.
When is the 10 year anniversary charge due?
No later than 6 months after the end of the month in which the anniversary fell.
Do assets added during the 10 years pay the full rate?
No. The rate is reduced by the quarters they weren't relevant property, so 20 quarters out of 40 pays half the rate.
What changed for IHT100d in April 2026?
100% Agricultural and Business Relief is now capped by relief allowances, with value above the allowance relieved at 50%.
