To get an inheritance tax reference number, apply to HM Revenue & Customs at least three weeks before you plan to make a payment, using either the online short form on GOV.UK or the paper Form IHT422. If the tax relates to a trust, you must use Form IHT122 by post instead. The reference links every payment to the correct estate and is required before you file the main return on Form IHT400.1GOV.UK. Apply for an Inheritance Tax Reference (IHT422)
Do You Need One at All
Not every estate needs a reference number. You only need one if the estate owes inheritance tax, which generally means the total value exceeds the nil-rate band of £325,000, a threshold frozen since April 2009 and set to stay there until at least April 2030.2GOV.UK. Inheritance Tax Thresholds and Interest Rates A residence nil-rate band of £175,000 may apply when a home passes to direct descendants, and transferable allowances between spouses or civil partners can push the combined threshold up to £1 million.
If the estate falls below the relevant thresholds and qualifies as an excepted estate, you won’t need a reference number and won’t file a full IHT400. Where tax is owed, request the reference as soon as you know, because HMRC says you need it at least three weeks before making any payment.3GOV.UK. Pay Your Inheritance Tax Bill – Get a Payment Reference Number
What to Gather Before You Apply
HMRC’s form asks for details about both the deceased and the person managing the estate, and it warns that a reference may not be allocated if any requested field is left blank.4GOV.UK. Application for an Inheritance Tax Reference Schedule IHT422
For the deceased, have ready their full legal name as it appeared on official records, their date of birth, their date of death, and their National Insurance number. The National Insurance number links the estate to the deceased’s lifetime tax records and is the single most common sticking point on the form. If you can’t find it, check old payslips, HMRC correspondence, or their personal tax account.
For yourself as the executor or administrator, you’ll need your full name and address, a telephone number, and your relationship to the deceased.
Applying Online
The online route is faster and is the one most executors should use. You start from the GOV.UK page “Pay your Inheritance Tax bill,” which links to a short online form.3GOV.UK. Pay Your Inheritance Tax Bill – Get a Payment Reference Number Submitting online gives you an immediate on-screen acknowledgment, and the reference is then issued by letter to the address you provided.
One limitation matters. The online form cannot be used where the inheritance tax relates to a trust. In that case, you need Form IHT122 instead, and it can only be submitted by post.5GOV.UK. Inheritance Tax: Payment Enquiries
Applying by Post
If you prefer paper, or can’t use the online form, download Form IHT422 from GOV.UK, fill it in completely, and send it to:
Inheritance Tax
HM Revenue and Customs
BX9 1HT4GOV.UK. Application for an Inheritance Tax Reference Schedule IHT422
A tracked postal service is worth the extra cost. Paper submissions don’t produce an immediate acknowledgment, and the form itself warns that incomplete applications may not receive a reference.
How Long It Takes
HMRC doesn’t publish an exact processing window. It simply tells applicants to apply at least three weeks before they plan to pay.3GOV.UK. Pay Your Inheritance Tax Bill – Get a Payment Reference Number Postal applications tend to run longer than online ones, so build in more time if you’re sending Form IHT422 or Form IHT122. The reference arrives by letter at the address on your application.
If the letter hasn’t arrived and a payment deadline is approaching, call the HMRC Inheritance Tax helpline on 0300 123 1072, or +44 300 123 1072 from outside the UK. The line is open Monday to Friday, 9am to 5pm, and closes on bank holidays.6GOV.UK. Inheritance Tax: General Enquiries Have the deceased’s details and the date you sent your application ready, since staff will need those to trace it.
Where the Reference Number Fits Next
Getting the reference is the first practical step in a short sequence.
Filing the IHT400
You need the reference before you send in the main return on Form IHT400. HMRC’s guidance on Form IHT422 says so directly: apply for the reference before submitting IHT400.1GOV.UK. Apply for an Inheritance Tax Reference (IHT422) If you wait until the return is ready and only then request a reference, you’re adding weeks of dead time. That delay can also feed into late-filing penalties, which start at £100 for a return up to six months late and escalate from there.7GOV.UK. IHTM36023 – Late Accounts: Penalties Chargeable
Making Payments
Every inheritance tax payment must carry the reference number so HMRC credits it to the right estate. You generally need to pay at least some of the tax before probate (called confirmation in Scotland) is granted.8GOV.UK. Pay Your Inheritance Tax Bill Without the reference, you can’t make a valid payment at all.
The Probate Code Is Different
Once you start paying, HMRC issues a separate unique probate code. That code is not the same as your inheritance tax reference number. The probate code is what you enter on the probate application form itself (PA1P if there is a will, PA1A if there is not).9GOV.UK. Applying for Probate: Before You Apply The reference number lets you pay; the probate code lets HMRC tell the court you’ve started paying. You need both, in that order.