There is a sentence that thousands of British couples will read over the next eighteen months, in financial advice columns and pension provider emails, and will not quite take seriously. The sentence is this: from 6 April 2027, if you die with an unused pension pot, and that pot passes to a partner you have not married, the partner pays inheritance tax on it at forty per cent above the nil-rate band.
If you have not had the conversation with your partner about what marriage means tax-wise, you are not unusual. Most cohabiting couples have not had that conversation. The statistical share of British adults living with a long-term partner outside marriage has more than doubled this century — the Office for National Statistics now estimates more than three million such couples in the United Kingdom — and the legal framework around inheritance and tax has, with one or two adjustments, stayed where it was in 1984.
The pension reform that takes effect from 6 April 2027 is not, on its face, about cohabitation. It is about inheritance tax. But because the spousal exemption — the rule that lets one spouse inherit any amount from the other without paying inheritance tax — applies only to married couples and civil partners, the reform's interaction with cohabitation is severe, mechanical, and entirely under-publicised.
What changes on 6 April 2027
Before 6 April 2027, an unused defined contribution pension pot — a SIPP, a workplace pension, a personal pension — sat outside the deceased's estate for inheritance tax purposes. It was held by the scheme administrator under discretionary trust, and on death, it passed to nominated beneficiaries free of inheritance tax. That was true whether the nominated beneficiary was a spouse, a partner, a child, a friend, or a sibling.
After 6 April 2027, the pension's value becomes part of the estate for the inheritance tax calculation. The estate's combined value — house, savings, investments, and now pensions — is measured against the £325,000 nil-rate band (frozen until 2031), the £175,000 residence nil-rate band (where applicable), and any transferred allowance from a previously deceased spouse. The excess is taxed at forty per cent.
If the pension passes to a spouse or civil partner, the spousal exemption applies and the inheritance tax charge is zero. If the pension passes to anyone else — including an unmarried partner of thirty years — the spousal exemption does not apply. The forty per cent rate, above the nil-rate band, applies in full.
The relationship has not changed. The household has not changed. The statute has changed. The household will now pay forty per cent on something it would not have paid forty per cent on six months earlier.
Who actually gets hit
Three groups will feel the change most acutely, and they are not the ones most coverage will focus on.
The first is the couple who chose not to marry on principle, or simply never got round to it, and who now own a modest house together and have worked-life pension pots. The arithmetic is straightforward. A house in the South East worth £450,000, two pensions totalling £200,000 between them, modest savings — and the household is already in a position where, on a first death, the surviving cohabiting partner faces an inheritance tax bill that simply would not have existed had the same two people signed a registration certificate at a council office.
The second is the older widowed or divorced individual who has formed a new partnership later in life, has not remarried, and whose original spouse's nil-rate band transfer is no longer available because that allowance has been spent on the previous estate. The combined effect of the new pension rules and the frozen allowances is harshest for this household, because the headroom available against the inheritance tax charge is at its narrowest.
The third is the blended family — a household where children from a previous relationship are intended to benefit from the pension. The non-spousal beneficiary issue applies. The administrative complexity grows. And the executor — who may themselves be a child from the previous relationship — now has to manage a six-month inheritance tax deadline while a scheme administrator works through nominations that may or may not be current.
What you can actually do about it
There are three responses to this change, and they should be considered in order.
The first, which most coverage will not lead with because it sounds glib, is to consider whether the household wants to marry. For couples who have stayed unmarried for reasons of inertia or personal preference rather than principle, the inheritance tax exposure created by the new rules is significant enough to be a material factor in the decision. The civil partnership route, opened to opposite-sex couples in 2019, provides the same tax treatment as marriage without the religious or social associations some couples wish to avoid. The cost of either is a registration fee. The tax benefit, for a household already over the nil-rate band, is the difference between zero and forty per cent on the pension's value.
The second is to review the pension's beneficiary nomination — formally known as the expression of wishes — and consider whether the structure of nominations still makes sense under the new rules. A pension nominated entirely to an unmarried partner sits in the worst position under the new regime. A pension nominated partly to a partner and partly to children may, depending on the children's age and tax position, produce a different combined outcome. The detail here is genuinely complex; the broad point is that the nomination structure was previously a minor administrative matter and is now a material tax planning decision.
The third is the lifetime gifting route. Gifts made more than seven years before death sit outside the estate. Gifts from surplus income, made regularly and not affecting the donor's standard of living, sit outside the estate without time limit. For households likely to breach the nil-rate band primarily because of the new pension inclusion, accelerated lifetime gifting becomes a meaningful lever.
What the Withholding Notice means for cohabitants specifically
Where the cohabiting case becomes operationally painful, beyond the headline tax charge, is in the administrative timeline. The executor of an estate must pay inheritance tax within six months of the end of the month of death (the account itself may follow up to twelve). Pension scheme administrators routinely take longer than six months to value pots, identify beneficiaries, and execute payments.
The Finance Act 2026 introduces a mechanism called the Withholding Notice. It allows the executor to instruct the pension administrator to freeze up to fifty per cent of the pension pot for up to fifteen months from the date of death, to protect the executor against personal liability for inheritance tax interest. For a married surviving spouse, the Withholding Notice is rarely necessary — the spousal exemption means the pension can pass cleanly. For a surviving cohabiting partner, the Withholding Notice is much more likely to be triggered, because the executor needs cover against a real and material inheritance tax bill.
The practical effect: a cohabiting partner who has just lost their long-term partner can find themselves, for up to fifteen months, with half of the household's pension capital frozen in a scheme administrator's account, unable to draw on it, and with no clear administrative recourse. This is the kind of friction families do not anticipate until it happens.
What we are not saying
We are not saying every cohabiting couple should marry. We are not in the marriage advice business and the personal reasons for the choice are legitimate. We are saying that the financial consequences of remaining unmarried changed materially with the Finance Act 2026, and that the change has not yet been priced into most households' thinking. The decision to remain unmarried is now a decision with a price tag attached, and the price tag is forty per cent of the unused pension above the nil-rate band.
We are also not saying this is the only thing to attend to. The cohabitation gap is one consequence of a broader reform that affects every household with a pension. The Withholding Notice mechanism affects every executor. The frozen thresholds bring more households into the inheritance tax net each year. The cohabitation case is the sharpest illustration of the new regime — not its only manifestation.
What to do before April 2027
Three things, in order, none of which require legal advice to begin.
Confirm your pension provider, the scheme reference, and the current value of the pot. Locate the latest expression of wishes — the document where you nominated who receives the pension on your death — and check that it still reflects your intentions. If the household is unmarried and the pension is nominated to the partner, understand that this nomination, which previously triggered no tax, will trigger a forty per cent charge from April 2027 if the estate exceeds the nil-rate band.
Tell your executor — or the person you would name as executor if you have not yet — where the pension information lives. The administrative window after death is short. The information they need to act inside that window must already be assembled. The work of finding becomes work that was already done.
And, finally, consider the marriage or civil partnership question on its merits, with the financial consequence priced in alongside everything else. The Finance Act 2026 did not intend to push cohabiting couples into civil partnerships. But it has changed the cost of remaining outside one, and that change is significant enough to deserve a calm, unhurried conversation between partners — before the rules take effect, and not after them.