ISA Bed and Breakfasting: Why It Doesn't Work for CGT

The terminology problem

There are three things that get muddled in everyday personal-finance writing:

1. Bed and breakfasting (old style): sell a share on day 1, rebuy on day 2, hoping to crystallise a loss or use the CGT allowance. Killed off by HMRC in 1998 with the introduction of the 30-day matching rule (TCGA 1992 s.106A).
2. Bed and ISA: sell from a General Investment Account, simultaneously rebuy inside your ISA. Allowed.
3. Bed and SIPP: the same idea but with a pension wrapper. Also allowed.

This article is mainly about #2 — bed and ISA — and why the #1 version "doesn't work" any more.

What the 30-day rule actually says

When you sell UK shares for CGT purposes, HMRC applies a strict matching order:

1. Same-day rule: if you sell and rebuy the same security on the same day, the sale is matched against that day's buys first.
2. 30-day rule: if you rebuy within 30 calendar days after the sale, the sale is matched against the 30-day repurchase next.
3. Section 104 holding: any remainder is matched against your average-cost pool of historic holdings.

The old "bed and breakfast" trick — sell on 5 April to use the allowance, rebuy on 6 April — fails because the rebuy on day 2 falls inside the 30-day window. The sale gets matched to the rebuy at virtually the same price, producing essentially zero gain and wasting your allowance.

Why bed and ISA legally sidesteps the rule

The 30-day rule applies when you "rebuy the same shares". When you rebuy inside an ISA, you are not buying as yourself in a personal capacity — you are buying as the ISA manager on your behalf. HMRC's CGT manual and decades of practitioner consensus treat this as a different acquisition for s.106A purposes. The sale in the GIA is therefore matched against your historic pool, not the ISA rebuy.

The same applies for:

• Selling and rebuying inside a SIPP.
• Selling and your spouse rebuying in their personal capacity — interspousal transfers are at no gain/no loss, then they buy.
• Selling and rebuying inside a limited company you control.

What is not allowed:

• Selling and rebuying the same shares in your own personal account inside 30 days.
• "Bed and partnering" via a settlor-interested trust (anti-avoidance rules block this).

Worked example — Liam shelters £40,000 of growth

Liam has £40,000 of a global equity fund in a General Investment Account, with a cost base of £25,000. So he has £15,000 of unrealised gain. He has not used any of his 2025/26 ISA allowance or CGT allowance.

Option A: do nothing.

Future dividends taxed at 8.75% / 33.75% / 39.35% above the £500 dividend allowance. Future gains taxed when realised at 18% / 24% above the £3,000 annual exemption.

Option B: bed and ISA the whole lot in one go.

• Sell £20,000 in the GIA → triggers gain of £20,000 × (15,000/40,000) = £7,500 gain.
• £7,500 gain minus £3,000 allowance = £4,500 taxable.
• Tax due (Liam is higher-rate): £4,500 × 24% = £1,080.
• Use the £20,000 proceeds to fund the 2025/26 ISA, repurchasing the same fund.

Outcome: Liam pays £1,080 now, but moves £20,000 plus the next year's growth into the tax-free wrapper forever.

Option C: split over two tax years.

• April 2026 (2026/27 allowance): sell £8,000 → gain £3,000 → fully covered by allowance → £0 tax. Bed-and-ISA into 2026/27 ISA.
• April 2027 (2027/28 allowance): sell £8,000 → gain £3,000 → £0 tax.
• And so on until the GIA is empty.

If Liam splits over 5 tax years, he pays zero CGT on the entire transfer, just by pacing.

For most investors, Option C beats Option B — the £3,000 allowance is use-it-or-lose-it annually, and there is no benefit to crystallising more than that unless you need the cash.

When bed and ISA gets complicated

1. Market movement during the trade

Bed-and-ISA is not instantaneous. Most platforms run it overnight or T+1 — the sale price and the rebuy price differ. In a fast-moving market you can end up with fewer shares in the ISA than you sold from the GIA. Some platforms offer "Bed and ISA at execution-only price match" but you usually accept a small slippage.

2. Funds vs ETFs vs shares

• Open-ended funds (OEICs): priced once a day. The sale and rebuy will be at the same NAV — clean trade.
• ETFs and shares: priced continuously. You will get two different intraday prices.

3. Dividend record dates

Selling just before a fund's ex-dividend date and rebuying just after means the dividend goes to the new holder of the original units — usually no longer you. Check the dividend calendar before initiating a bed-and-ISA on a near-payable fund.

4. Share Pooling for AIM and unit trusts

The Section 104 pool calculation can produce surprising base-cost figures if you've been buying steadily over years. Many platforms now show your computed CGT base cost. If yours doesn't, you may need to reconstruct from contract notes before bed-and-ISA.

The simpler-than-it-looks practical playbook

For most people with GIA holdings and unused ISA allowance, bed-and-ISA every April is the obvious move. The rough rhythm:

1. In March: check unrealised gains on each GIA holding. Identify which holdings would crystallise roughly £3,000 of gain.
2. In early April (new tax year): open your platform's bed-and-ISA tool. Most charge £0–£5 per holding moved.
3. Choose the holdings to move first: highest dividend-yielding investments and most volatile (largest unrealised gain) are good candidates.
4. Recheck after the trade that your CGT for the year is within the £3,000 exemption.

Over a decade, this can move £150,000–£200,000 of holdings into the ISA wrapper at zero CGT cost.

Spousal bed and ISA — the high-allowance hack

Married couples and civil partners can transfer assets between themselves at no gain / no loss. Combined with bed-and-ISA this allows:

• £20,000 ISA per person per year = £40,000 ISA shelter for the couple annually.
• £3,000 CGT exemption per person = £6,000 combined annual gain sheltered.

The mechanics: transfer half the GIA holding to your spouse first (gift), then each of you bed-and-ISAs your own half into your own ISA. This effectively doubles the speed at which a couple can drain a GIA into ISAs.

See our Marriage Allowance guide for related spousal optimisation.

Why this got more important in 2025/26

The CGT annual exemption used to be £12,300. Dividends used to enjoy a £2,000 allowance. Today:

Every year more of an ordinary investor's portfolio bumps into the GIA tax-net. Bed-and-ISA is the cleanest, most boring, most reliable way to escape that net. It's why mainstream platforms (Hargreaves, AJ Bell, Vanguard UK, Fidelity, Interactive Investor) all market it as a flagship spring feature.

What bed-and-ISA cannot do

• Cannot shelter foreign-currency gains in non-ISA-eligible exchanges.
• Cannot move a holding not eligible for an ISA (e.g. AIM shares restricted by your provider, some niche investment trusts).
• Cannot create a CGT loss if the actual gain is positive — losses still follow the share-matching rules.
• Cannot avoid stamp duty on the repurchase of UK shares (0.5% — usually trivial for funds but real for direct equities).

Try the calculator

To work out your gain and remaining allowance before bed-and-ISA:

To project the tax-free growth once your holding is inside the wrapper:

Sources

• HMRC: Capital Gains Tax: shares and Section 104 pooling (CG51560+)
• HMRC: Individual Savings Accounts rules — gov.uk
• Taxation of Chargeable Gains Act 1992, s.106A (anti-bed-and-breakfast rule)
• HMRC: Capital Gains Tax allowance and rates — gov.uk