How to Calculate Your UK Inheritance Tax Liability

This guide explains the calculation step by step, using clear definitions and worked examples.

• UK Inheritance Tax is charged at 40 percent on the value of your estate above available allowances.
• Long-term residency determines whether worldwide assets or only UK assets are taxed.
• Most individuals have at least a £325,000 Nil Rate Band. Many also qualify for the £175,000 Residence Nil Rate Band.
• Allowances can usually be transferred between spouses or civil partners.
• Estates above £2 million start to lose the Residence Nil Rate Band.
• Accurate calculation requires factoring in lifetime gifts made in the seven years before death.

Domicile is a long-term legal concept based upon a person’s country of birth and their father. This principle used to be utilised for inheritance tax purposes but has now been changed to be based on long-term residency.

Long-term Residency is a legal concept. For IHT, individuals who are UK long-term resident, are taxed on their worldwide assets.

You are treated as a long-term UK resident for a tax year if you were UK tax resident for the previous 10 consecutive years, or for at least 10 years in total within the previous 20 years.

Tax residence is about where you live year to year. It does not determine IHT exposure on its own.

Inheritance Tax is governed by long-term residency. This distinction drives which assets are included in the calculation.

If you become tax resident outside of the UK for more than ten years (when you previously were a long-term UK tax resident) you will no longer be liable to UK inheritance tax on your worldwide assets, only your UK assets.

Your estate includes:

• Property
• Investments and savings
• Business interests
• Personal possessions
• Certain trusts and trust interests
• Gifts made within seven years of death

For UK long-term resident individuals, this is a worldwide calculation. For individuals who are not long- term resident, only UK-situated assets are included.

Every individual has a standard Nil Rate Band of £325,000.

This means the first £325,000 of your estate is taxed at 0 percent.

If you are married or in a civil partnership and your spouse left unused allowance on their death, this can usually be transferred, potentially doubling the NRB to £650,000.

You may also qualify for the Residence Nil Rate Band of up to £175,000 if:

• You own or owned a qualifying UK residential property, and
• It is left to direct descendants (children, grandchildren)

Like the NRB, unused RNRB can usually be transferred between spouses or civil partners.

If your estate exceeds £2 million, the RNRB is reduced by £1 for every £2 over that threshold.

At £2.7 million, the RNRB is lost entirely.

Once allowances are deducted, the remaining value of the estate is taxed at 40 percent.

• Total estate on second death: £1,500,000
• Combined NRB: £650,000
• Combined RNRB: £350,000
• Total allowances: £1,000,000

Taxable estate:
£1,500,000 minus £1,000,000 = £500,000

Inheritance Tax due:
£500,000 x 40 percent = £200,000

• Estate exceeds £2.7 million
• Full loss of Residence Nil Rate Band
• Combined NRB only: £650,000

Taxable estate:
£3,000,000 minus £650,000 = £2,350,000

Inheritance Tax due:
£2,350,000 x 40 percent = £940,000

Certain gifts made during your lifetime reduce your estate, but only if you survive long enough.

• Gifts within seven years of death may be taxable
• Taper relief can reduce tax on gifts made more than three years before death
• Gifts with retained benefit usually remain fully taxable

This is one of the most common areas of miscalculation.

Most people focus on the 40 percent tax rate and ignore the structural drivers.

The real exposure is driven by domicile status, allowance loss above £2 million, and poor sequencing of gifts. Spreadsheet-style calculations miss these risks entirely.

• Confirm your long-term residency position
• List worldwide assets and liabilities
• Identify transferable allowances from a spouse or civil partner
• Check whether the Residence Nil Rate Band applies or is tapered
• Review gifts made in the last seven years
• Stress-test future estate growth, not just today’s value

• Assuming residence and domicile are the same
• Ignoring allowance tapering above £2 million
• Making last-minute gifts without understanding gift-with-reservation rules
• Treating online calculators as a substitute for planning

Inheritance Tax is calculated using a simple formula, but the inputs are complex and highly sensitive to personal circumstances.

Understanding how the calculation works is the foundation. Reducing the tax legally requires structured, forward-looking planning, not last-minute arithmetic.

Disclaimer. The information in this article is general in nature and does not constitute personal financial, tax, or legal advice. UK tax legislation changes frequently, and the specific application of any rule or strategy depends on individual circumstances. Figures, thresholds, and reliefs mentioned are correct as of the 2026 to 2027 tax year unless otherwise stated. Before acting on any information here, consult a qualified adviser who has reviewed your full situation. Bluebond Tax Planning provides personal recommendations only under a signed client agreement, following a full review. Bluebond Tax Planning operates under UK legal frameworks and recognised professional conduct standards. Tax planning and legal work are not FCA regulated.