About
Probate Calculator is a free UK Inheritance Tax calculator. It exists because the free tools available were either too simple to be trusted or too obviously a form standing between you and an email capture.
What we set out to do
Three things, in this order.
Be the best free answer to "how much Inheritance Tax will my estate pay?" That means getting the order of operations right, modelling the rules that actually move the number, and showing the working so you can check it.
Say what we don't cover. Trusts, the residence band downsizing addition, gifts with reservation of benefit, quick succession relief, double taxation relief, non-UK domicile cases, woodlands relief and the instalment option are all outside the calculator. They're listed on the homepage and flagged in the guides where they're relevant. A tool that pretends to handle everything is less useful than one that is clear about its edges.
Give you the full result, free, with no gate. No sign-up, no email wall, no "enter your details to see your result". The calculation runs entirely in your browser — the figures you type are never sent to us, and we couldn't see them if we wanted to.
How the figures are kept current
Every rate and threshold lives in a single file with a source link and a "last verified" date against each value. There are no numbers hard-coded in the calculation logic. One annual review updates that file and the whole site follows, including the "rules current as at" stamp in the footer.
Rules on this site are current as at 9 October 2026.
A handful of values are flagged as needing confirmation against live HMRC and GOV.UK guidance:
- Business & Agricultural Property Relief £1m allowance (from 6 April 2026)
- Nil-rate band freeze end date
We'd rather tell you that than quietly present an unverified figure as settled.
How the calculation is tested
The calculation engine is a standalone module with no interface attached to it, which means it can be tested properly. It has a suite of unit tests built from HMRC's worked examples plus the edge cases that break naive implementations:
- Estates exactly at a threshold, and a pound either side
- The £2m residence band taper at its boundaries, including the point where it wipes the allowance out entirely
- The taper measured on the estate before reliefs — which is what stops Business Relief from rescuing the residence band
- Gifts set against the nil-rate band oldest first, with taper relief applied to the tax rather than the gift
- The annual exemption with exactly one year's carry-forward, not two
- A gift made precisely N calendar years before death, which naive date arithmetic puts in the wrong taper band
- 100% to a spouse, 100% to charity, and the 36% reduced rate at the pound either side of the 10% hurdle
Who's behind it
We are a team of software engineers with extensive experience across banking, finance, and data security. We build software designed to eliminate bureaucracy and simplify complex financial processes. We launched this standalone calculator first to give families instant, transparent calculations before diving into the full administration process.
We're building Executr, to give executors a calm, structured way to navigate probate—from generating HMCTS and HMRC forms to tracking assets and managing estate tasks.
Getting in touch
Corrections are especially welcome. If you think a figure is wrong or a rule is misapplied, tell us — we'd rather fix it than defend it.
The necessary caveat
This site provides general information and an estimate. It is not tax, legal or financial advice, and it does not recommend any product or course of action. Please read the full disclaimer, and take professional advice before acting on anything material.