AIM inheritance tax portfolios hold shares in companies traded on the Alternative Investment Market so that, on death, those shares attract Business Relief and pass to beneficiaries at a reduced tax cost. From 6 April 2026, qualifying AIM shares get 50% Business Relief rather than the 100% relief available before that date. Half the value of qualifying shares is sheltered; the other half is taxed at the standard 40% inheritance tax rate. The effective rate on qualifying AIM holdings is therefore 20%, compared with 40% on most other investments above the nil-rate band.
The relief is not automatic. It depends on which companies you hold, how long you have held them, and whether your executors claim it correctly after death.
How Business Relief Applies to AIM Shares
Business Relief reduces the taxable value of qualifying business assets in a deceased person’s estate. The rules sit in sections 103 to 114 of the Inheritance Tax Act 1984. Section 104 sets a default relief rate of 50% for relevant business property, with some categories (interests in unincorporated businesses, for example) qualifying for 100% up to an allowance cap.1Legislation.gov.uk. Inheritance Tax Act 1984 – Section 104
AIM shares fall into a specific slot: unquoted shares traded on a recognised stock exchange. Although AIM is run by the London Stock Exchange, it operates as a multilateral trading facility rather than a listed market, and shares traded solely on AIM are treated as unquoted under section 105(1)(aa).2LexisNexis. Inheritance Tax Act 1984 – Section 105 If a company on AIM is also listed on a main stock exchange anywhere in the world, it loses that unquoted classification and the associated relief.
What the April 2026 Change Does in Pounds
Before 6 April 2026, AIM shares qualified for 100% Business Relief, removing inheritance tax on those holdings entirely. From that date, the government cut the relief to 50% for shares admitted to trading on a recognised stock exchange but not listed on one, the category that captures AIM.3GOV.UK. Changes to Agricultural Property Relief and Business Property Relief
Take a £500,000 AIM portfolio held by someone whose nil-rate band is already used elsewhere in the estate. Business Relief now shelters £250,000. The remaining £250,000 is taxed at 40%, producing a £100,000 bill. Under the old rules the bill was zero. Without any Business Relief the same portfolio would face £200,000 of tax, so the reduced relief still halves what would otherwise be due.
Business Relief works separately from and in addition to the £325,000 nil-rate band and the £175,000 residence nil-rate band, both frozen until April 2030.4GOV.UK. Inheritance Tax Thresholds and Interest Rates5GOV.UK. Inheritance Tax Nil-Rate Band, Residence Nil-Rate Band From 6 April 2028
Which AIM Companies Actually Qualify
Not every AIM company gets the relief. The company must be engaged primarily in trading. If its business consists mainly of holding investments, dealing in securities, or dealing in land and buildings, its shares are not relevant business property. This is the single most common reason AIM shares fail to qualify, and it catches investors who assume any AIM listing is enough.
HMRC looks at what a company actually does, not what it calls itself. A technology firm earning its revenue from software sales is trading. A firm structured as a technology company but earning most of its income from property or investment returns is not. Portfolio managers running AIM inheritance tax services screen against these criteria before including a company, but investors picking their own stocks need to check each one’s revenue mix.
Excepted Assets Within a Qualifying Company
Even when a company passes the trading test, HMRC can strip out the value of specific assets inside it that are not used for the trade. Under section 112, any asset not used wholly or mainly for business purposes during the two years before death, and not needed for future business use, is an “excepted asset” and is removed from the Business Relief calculation.6GOV.UK. Shares and Assets Valuation Manual – IHT Business Property Relief: Excepted Assets
Surplus cash is the usual trigger. HMRC assesses whether the company’s cash balance is excessive relative to its trading needs by asking how much cash it uses regularly, what its short-term requirements are, and whether the balance moves with the business cycle.7GOV.UK. Shares and Assets Valuation Manual – IHT Business Property Relief: Practical Approach Cash sitting idle is classed as a non-business asset. The headline 50% relief may not apply to the full share value if the underlying company holds material non-trading assets.
The Two-Year Holding Period
Business Relief only applies to shares owned for at least two years before death. Section 106 is blunt: property is not relevant business property unless the transferor owned it throughout the two years immediately before the transfer of value.8GOV.UK. Shares and Assets Valuation Manual – Section 106 IHTA 1984 Buy qualifying AIM shares, die 18 months later, and the estate gets no relief on them. They enter the estate at full value and face 40% above the nil-rate band.
The clock starts on the date you acquire the shares. The contract note from the broker is the primary evidence of that date, so those records need keeping.
Replacement Property
You do not have to hold the same shares for the whole two years. Section 107 allows replacement: if you sell one qualifying holding and buy another, the ownership periods can be combined, provided you have owned qualifying business property for a total of at least two years within the five years before death.9Legislation.gov.uk. Inheritance Tax Act 1984 – Section 107 The replacement must itself be property that would have qualified, and the relief on the new holding cannot exceed what would have applied to the original.
This flexibility lets portfolio managers swap out companies that stop meeting the trading test without restarting the clock. The five-year lookback is the constraint: qualifying ownership outside that window does not count.
Shares Passing to a Spouse
When qualifying AIM shares pass from a deceased spouse to a surviving spouse, the survivor inherits the deceased’s ownership period under section 109. The two-year clock does not reset on death. Lifetime gifts between spouses work differently: the receiving spouse must hold the shares for two years in their own right before Business Relief becomes available.
Holding AIM Shares in an ISA
AIM shares can be held inside a stocks and shares ISA. While you are alive, dividends and capital gains inside the ISA are free of income tax and capital gains tax. On death, the AIM shares inside the ISA can still qualify for Business Relief.
The combination remains useful under the 50% rules. An AIM ISA removes income and gains tax during your lifetime, and Business Relief brings the effective inheritance tax rate on qualifying shares down to 20%. Investments inside a standard ISA are fully exposed to inheritance tax at 40%, so the AIM ISA structure keeps a clear advantage even after the April 2026 reduction.
To move an existing stocks and shares ISA into an AIM-focused portfolio, you can use a specie transfer, re-registering the assets with a new provider rather than selling and rebuying. That preserves the ISA wrapper and avoids triggering a taxable event.
Weighing the Tax Saving Against the Investment Risk
The tax saving is only worth having if the underlying investment holds its value. AIM companies are smaller, less liquid, and more volatile than main market shares. Prices can move sharply on modest volumes, and selling a large holding quickly may mean accepting a steep discount. Many AIM inheritance tax portfolios hold 20 to 30 companies, which concentrates the impact if a few perform badly.
Eligibility can also change. A company that qualifies today might not qualify tomorrow if it shifts toward investment holding, builds up excess cash, or moves to a main market listing. Managers monitor this, but there is no guarantee every company stays eligible right through to death.
Capital loss is a real prospect. An investor saving 20% in effective inheritance tax while losing 30% of their capital is worse off than someone who paid the tax on a more stable portfolio. Fees compound the point: annual management charges on professionally run AIM inheritance tax portfolios typically fall in the range of 0.75% to 1.5%, plus dealing costs when shares are traded. Over a decade that can add 7.5% to 15% of the initial investment in management charges alone.
Tax During Your Lifetime
Outside an ISA, dividends from AIM shares are taxable as dividend income, and gains on sale are subject to capital gains tax. For 2025/26 the dividend allowance is £500 and the capital gains annual exempt amount is £3,000 for individuals. Amounts above those are taxed at the rates for your income band.
On death, no capital gains tax is charged. Beneficiaries acquire the shares at market value on the date of death rather than at the price you originally paid, so unrealised gains built up during your lifetime are wiped out for capital gains tax purposes. Alongside Business Relief on the inheritance tax side, that makes qualifying AIM shares among the more tax-efficient assets to hold at death.
What Executors Have to Do to Claim the Relief
The tax benefit is not automatic. Executors have to claim Business Relief when they report the estate.
Business Relief on AIM shares is claimed using form IHT412, submitted as a supplementary schedule alongside the main IHT400 inheritance tax account.10GOV.UK. Inheritance Tax: Unlisted Stocks and Shares and Control Holdings (IHT412) The form asks for each shareholding, the date of acquisition, the value at death, and the amount of relief being claimed. Contract notes or portfolio statements from the fund manager provide the evidence.
HMRC checks whether each company was still carrying on a qualifying trade at the date of death. Fund managers can usually issue a confirmation letter, but HMRC may ask for more. If a claim is rejected, because a company had drifted into non-qualifying activities or because the two-year holding period was not met, the estate owes inheritance tax on the full value of those shares.
The IHT400 must be submitted within 12 months of the date of death, and generally before applying for probate. Inheritance tax itself is due by the end of the sixth month after the month of death. Someone who dies in March, for example, has a payment deadline of 30 September. Interest runs from that deadline on anything still outstanding, and HMRC can impose penalties for late filing without a reasonable excuse.11GOV.UK. How to Value an Estate for Inheritance Tax and Report Its Value Getting date-of-death valuations for less liquid AIM stocks can take longer than for main market shares, so executors should request them from the fund manager early.