Survivorship Clause in a Will UK (2026): What It Does, the Commorientes Rule & the IHT Trap

A survivorship clause is a condition in a will that requires a beneficiary to survive the testator by a specified period — usually 28 or 30 days — before they can inherit. If the beneficiary dies within that period, the gift fails and falls into the residue or to named substitute beneficiaries. The purpose is to avoid double probate: if two people die in quick succession, running two full probate processes for the same assets is expensive and time-consuming. A survivorship clause ensures the estate only passes once to someone who actually survives long enough to benefit.

The commorientes rule (Latin: 'those dying together') is the legal presumption that applies when two or more people die in circumstances where the order of deaths cannot be established — for example, in a car accident. Under section 184 of the Law of Property Act 1925, where the order cannot be established, the elder is presumed to have died first and the younger to have survived. This affects who inherits whose estate. Separately, section 4(2) of the Inheritance Tax Act 1984 treats simultaneous deaths as exactly simultaneous for IHT purposes — creating a crucial difference between the property law and tax law positions.

Here is the problem: mirror wills often include a 30-day survivorship clause. When both spouses die together (commorientes), the Law of Property Act says the younger survived the elder. But the survivorship clause says the beneficiary must survive by 30 days — which cannot be confirmed in simultaneous deaths. So the clause prevents the transfer: the estate passes as if the spouse predeceased, directly to children. But the Inheritance Tax Act treats the deaths as simultaneous — so the spouse IHT exemption cannot be applied. The result can be an unexpected IHT bill on the first estate.

The fix is a commorientes carve-out clause: 'The survivorship condition shall not apply if the testator and the beneficiary die in circumstances making it uncertain which of them survived the other.' This negates the survivorship clause in simultaneous death cases, allowing the property law presumption to apply and preserving the spouse IHT exemption. This is now standard drafting practice in professionally drafted wills. If your will was drafted before roughly 2000, or was a DIY document, check whether it includes this carve-out.

The most common periods are 28 or 30 days. The STEP standard provisions used by solicitors default to 30 days. Some wills specify 1 month; longer periods (3–6 months) are unusual. For most purposes, 28–30 days is appropriate: long enough to avoid double probate if deaths are separated by days, short enough to be reasonable. Longer periods increase the risk that a gift fails and falls into residue when the beneficiary dies shortly after the testator — potentially frustrating the testator's real intentions.

A survivorship clause can be applied globally or to specific gifts. Most wills apply it to the primary gift to the spouse or civil partner and to residuary beneficiaries. Specific cash gifts (pecuniary legacies) may or may not be subject to the condition. If the survivorship condition is not met, the gift usually falls into residue. Naming substitute beneficiaries avoids this problem — if the primary beneficiary does not survive the required period, the substitute takes instead.

For most wills, yes — a 30-day survivorship clause with a commorientes carve-out is good practice. It prevents double probate without the IHT trap. Ensure the clause explicitly states it does not apply when the order of deaths is uncertain. A professionally drafted will kit should include this automatically. If you have an older DIY will or one drafted before 2000, check whether the carve-out is present — if it is not, consider having your will reviewed.