UK IHT Calculator Guide 2026/27 — Estate, Gifts and Allowances

The UK IHT Calculator→ is a starting point for estimating how an estate might be exposed to Inheritance Tax (IHT). It is most useful when you use it to organise the facts: property, savings, investments, personal belongings, gifts made in the last seven years, a qualifying home, spouse or civil-partner history and charitable gifts. It is not a substitute for a probate valuation, the IHT400 account, a solicitor or HMRC’s final calculation.

The existing UK Inheritance Tax guide explains the law and allowances in more detail. This page addresses a different search intent: how to prepare and interpret a calculator estimate without entering the wrong estate value, counting an allowance twice or treating a simplified output as an eligibility decision.

For deaths in the 2026/27 tax year, the published basic nil-rate band is £325,000. The residence nil-rate band (RNRB) can be up to £175,000 when a qualifying residence passes to direct descendants, subject to the conditions and taper. The GOV.UK thresholds material says these levels and the RNRB taper threshold are fixed through the periods stated in the current legislation and guidance. Always use the official HMRC source for the relevant date of death rather than copying a threshold from an old calculator or article.

What the calculator is estimating

At a high level, an IHT scenario compares a chargeable estate with the nil-rate bands and any applicable exemptions or reliefs. A simplified model may begin with the estate value, subtract or account for a residence allowance, consider spouse or civil-partner transfer, include relevant gifts and apply a tax rate to the amount above the available threshold. That sequence is useful for orientation, but the legal calculation depends on the history and classification of each transfer.

The tool's main inputs are designed around common planning questions:

The result should be labelled as an estimate. If a result is close to a threshold, small valuation changes, debts, gifts or relief conditions can change the outcome. Use a range rather than entering a false level of precision.

Step 1: build an asset inventory

Start with a list of assets rather than the calculator. Include the main residence, other property, bank and building-society accounts, ISAs and investments, business interests, agricultural property, vehicles, valuable possessions, life insurance that is not held in trust, loans owed to the deceased and any pension or death benefit that may be relevant under the date-of-death rules.

The value for IHT is not always the same as the figure on a balance sheet or an online account. Property usually needs an open-market valuation at the relevant date. Shares may need a market value and, for private or restricted interests, evidence of the appropriate valuation. Household goods and personal possessions should be considered as part of the estate rather than silently treated as worthless.

Also list debts and liabilities that are genuinely owed and deductible under the rules. A mortgage, loan, funeral expense or other liability can affect the net estate, but the exact deduction conditions matter. Do not enter a debt merely because it appears in a household budget, and do not deduct costs twice in the calculator and in a later professional calculation.

The GOV.UK estate valuation guidance explains that full estate details include assets, debts, gifts, reliefs and exemptions. Use that as the inventory checklist before trusting the calculator output.

Step 2: understand the nil-rate band

The basic nil-rate band is the threshold available against the estate and certain lifetime transfers. For the 2026/27 period covered here, HMRC publishes it as £325,000. The calculator may display that as a default, but it cannot know whether earlier lifetime transfers have already used some or all of it.

An outright gift to an individual is generally a potentially exempt transfer: if the donor survives seven years, it can become exempt; if the donor dies within seven years, it can become chargeable subject to the available thresholds, exemptions and reliefs. Gifts are therefore not simply “outside the estate” because they left the bank account. Enter relevant gifts with their dates and values, and keep evidence of what was given and to whom.

The annual gift exemption, small-gift exemption, wedding or civil-partnership gifts and normal expenditure out of income have different conditions. A simplified calculator may apply one annual amount to an input, but it cannot reconstruct a lifetime pattern of gifts or decide whether regular payments were genuinely made from surplus income without reducing the donor’s normal standard of living.

Taper relief is also commonly misunderstood. It can reduce the tax charged on a failed gift after the relevant time has elapsed, but it does not make every gift tax-free, does not restore a used nil-rate band and does not eliminate the need to include the transfer in the estate history. The gifts guide covers these distinctions.

Step 3: test the residence nil-rate band

The residence nil-rate band is not a general property allowance. It is linked to a qualifying residence passing to direct descendants and is subject to the statutory conditions. The maximum published RNRB for the relevant period is £175,000, but the calculator should not treat the full amount as automatic.

Check four questions:

1. Was there a qualifying residence or a qualifying former residence under the relevant rules?
2. Does it pass to direct descendants as defined by the rules?
3. Is the estate below the RNRB taper threshold, or is the allowance reduced by the taper?
4. Is there unused RNRB from a predeceased spouse or civil partner that can be transferred?

If the home is worth less than the maximum RNRB, the allowance can be limited by the qualifying residence value. If the residence is not passing to a qualifying descendant, the RNRB may not apply even if the estate includes a valuable home. Downsizing and selling the home before death can require a separate review; do not switch the “home to descendants” input on simply because the family intends to help children in the future.

Step 4: consider spouse and civil-partner transfers

Transfers between spouses or civil partners are generally treated differently from gifts to other people, and unused nil-rate bands may be transferable to the survivor. This is why a calculator can show a materially different result when the “married or civil partner” input changes. It is a planning prompt, not proof of the available allowance.

The evidence may include the first death certificate, the first estate account, the will, the assets passing to the spouse or civil partner and any use of the first person’s allowance. A couple is not automatically entitled to a fixed combined tax-free estate. The residence, beneficiaries, gifts, reliefs, ownership and dates still need checking.

The calculator should show whether it is assuming full transfer, partial transfer or no transfer. If the interface does not expose that distinction, treat the result as a broad illustration and obtain a professional calculation before relying on it.

Step 5: record gifts instead of guessing

For each gift, record the date, recipient, value at the date of the gift, asset transferred, whether the donor retained a benefit, and whether an exemption was claimed. Include gifts of cash, property, investments, possessions and transfers at undervalue. A home sold to a child for less than market value can create a gift equal to the value given up.

The calculator's “years ago” field is useful for scenario timing but is not a substitute for the actual date. A gift made near a tax-year boundary, or a sequence of gifts to the same person, may interact with annual exemptions and earlier transfers. Retained use of a gifted property can also create a gift-with-reservation issue. Keep the full history even when the simplified output says no tax is due.

If the donor is alive and wants to make a major gift, the calculator should be the beginning of the discussion, not the conclusion. Consider the donor’s future care needs, the recipient’s tax position, control of the asset, relationship risk and the possibility that the donor will need the money later. Tax efficiency is not the same as financial security or a suitable legal arrangement.

Step 6: charity and the reduced rate

A qualifying charitable gift can reduce the chargeable estate. In some circumstances, leaving at least 10% of the relevant net estate to charity can allow a reduced IHT rate of 36% on the qualifying amount. The GOV.UK charity guidance and the will wording control the result.

Enter a charitable amount only when it reflects the will or a deliberate scenario. Do not use the charity field to reduce the estate simply because an organisation is non-profit. The calculator may show a simplified reduced-rate result, but it cannot establish the net-value calculation, qualifying charity, exemptions, debts or wording needed for the legal test.

Step 7: pensions and the 6 April 2027 boundary

Pensions require a date-sensitive input. HMRC's technical note says that from 6 April 2027, most unused pension funds and pension death benefits will be brought within the value of the deceased person’s estate for IHT purposes. The change applies to deaths on or after that date, and the detailed exceptions, reporting and payment process must be checked against the latest official guidance.

This means a calculator used for a 2026/27 planning discussion should display the date boundary clearly. Do not use a current assumption about an unused pension fund to estimate a death after 6 April 2027 without including the legislated reform. Equally, do not apply the future rule retrospectively to a death before that date.

The UK inherited-pension guide explains the change separately. A pension balance can also have Income Tax consequences for the beneficiary, and death-in-service benefits or scheme-specific exclusions may require separate treatment. The calculator should flag uncertainty rather than pretend that one pension input captures every arrangement.

Business, agricultural and trust assets

Business Relief, Agricultural Relief and trust charges are not safely represented by a simple “relief yes/no” switch. Eligibility can depend on the asset, ownership period, business activity, agricultural use, transfer history, rate of relief and date of death. The current policy also includes changes from 6 April 2026 to the 100% relief allowance for qualifying business and agricultural property, so old planning articles can be stale.

If the estate includes a trading business, farm, shares in a private company, a trust or a large agricultural asset, use the calculator only for a no-relief and broad-relief range. Keep the relief assumptions visible and read the official Business Relief guidance and Agricultural Relief guidance. A professional valuation and legal review are usually more important than a more elaborate spreadsheet.

Interpreting the output

Read the calculator output in layers:

1. Gross estate — does the starting inventory include all assets and exclude nothing twice?
2. Net estate — are debts and liabilities supported and treated once?
3. Available bands — is the basic band, residence band and any transferred allowance clearly identified?
4. Lifetime transfers — are gifts included with their actual dates and exemptions?
5. Taxable amount — does the rate and charity assumption match the official rule being modelled?
6. Cash deadline — could the executor pay before probate, or would an instalment or postponed-payment route be needed?

If the result changes significantly when one input moves by a small amount, the estate is threshold-sensitive. Preserve both the lower and higher valuation case. HMRC may use professional valuations or revise the calculation if assets are later agreed at a different value.

Estate reporting and payment timing

If IHT is due, GOV.UK says it must normally be paid by the end of the sixth month after the person died to avoid interest. A payment towards IHT is usually needed before a grant of representation, although payment by instalments or postponement can apply in particular circumstances. The estate must also be valued and the required account submitted; a calculator does not prepare IHT400 or obtain probate.

GOV.UK's estate guidance says full details are generally reported within one year when IHT is due or full details are required. Keep the payment deadline and reporting deadline separate in your planning notes. The first is a cash-flow problem; the second is an estate-reporting obligation. If the estate cannot release cash because property or investments have not yet been sold, review the official payment-on-account, instalment and grant-on-credit routes rather than delaying without advice.

A practical IHT calculator workflow

The strongest result is a clear audit trail: every input has a source, every assumption is labelled, and every uncertain relief is isolated. Save the scenario beside the will, valuation evidence, gift records, pension statements and ownership documents. If those records cannot support the inputs, the output is not ready for probate or a major lifetime gift.

Common mistakes

Entering only the family home

IHT applies to the estate, not just the house. Savings, investments, possessions, business interests, insurance and relevant pensions or gifts can materially change the result.

Treating RNRB as a second general allowance

The residence band depends on the home, beneficiary, estate value and transfer history. It is not available simply because someone owns a property.

Applying taper relief to the whole estate

Taper relief relates to certain chargeable gifts and the time between the gift and death. It does not generally reduce the tax on the death estate itself.

Ignoring gifts because the money is gone

Relevant lifetime gifts can use the nil-rate band or become chargeable if death occurs within seven years. Keep the record even when the calculator initially shows no tax.

Assuming pensions are always outside IHT

The rules change for most unused pension funds and death benefits from 6 April 2027. Check the date of death and the scheme-specific exceptions.

Treating the estimate as probate approval

The calculator cannot issue a payment reference, complete IHT400, verify valuations or obtain a grant of representation. It is a planning and preparation tool.

Frequently Asked Questions

Official sources

This guide uses current HMRC and GOV.UK material for IHT thresholds, gifts, residence relief, estate reporting, payment deadlines, charity, business and agricultural relief, and the 2027 pension change:

• How Inheritance Tax works
• Inheritance Tax thresholds and interest rates
• Inheritance Tax thresholds through 2030/31
• Rules on giving gifts
• Work out Inheritance Tax due on gifts
• Residence nil-rate band
• Pay your Inheritance Tax bill
• Value an estate and report its value
• Inheritance Tax on pensions technical note
• Business Relief for Inheritance Tax
• Agricultural Relief for Inheritance Tax
• Charity and Inheritance Tax