What is the 30-day rule in UK CGT?

The "Bed & Breakfast" anti-avoidance rule. If you sell shares + repurchase the same shares within 30 days, HMRC matches the disposal against the new acquisition (not against your existing pool). This prevents harvesting losses by selling Friday + repurchasing Monday. The rule applies to all CGT-eligible assets including crypto, ETFs and individual stocks.

How do I crystallise a gain using the AEA legally?

Use ISA wrapper or spouse transfer. Bed-and-ISA: sell shares from general account, immediately repurchase same shares inside ISA. The disposal crystallises the gain (potentially within AEA), and the new ISA holding grows tax-free forever. Spouse transfer: gift shares to spouse before they sell - uses both your AEAs. Direct sell-then-repurchase in same account triggers the 30-day rule.

What's the order of share matching for CGT?

(1) Same-day rule - match against acquisitions made the same day. (2) 30-day Bed & Breakfast rule - match against acquisitions in 30 days following disposal. (3) Section 104 pool - all remaining holdings averaged into weighted-average cost. Each rule applies in sequence - same-day takes priority, then 30-day, then pool.

Can I use bed-and-ISA to reset cost basis?

Yes. Sell shares from general account (triggers CGT), immediately buy same shares inside ISA. The disposal uses your £3,000 AEA + any allowable losses. Future gains/dividends on the ISA-held shares are tax-free. Strategy works best for shares with gain less than AEA, allowing repeated annual transfers without tax. Approximately £3,000 of gains can be sheltered per year per person.

How does spouse transfer save CGT?

Inter-spouse transfers are tax-free (treated as no-gain-no-loss). After transfer, your spouse owns the asset at your original base cost. They can then sell using their own AEA (£3,000 each). Combined, married couple shelters £6,000 of gains per year vs single AEA. Common strategy for liquidating investments before retirement.

What CGT rates apply in 2026/27?

Two rates depending on which Income Tax band the gain falls into (when added to your income): basic-rate band = 18%, higher-rate band = 24%. £3,000 AEA per individual per year. Reporting + payment via Self Assessment by 31 January following tax year end. Property disposals: 60-day reporting + payment via gov.uk/report-and-pay-cgt.

Does the 30-day rule apply to swaps between funds?

Yes if it's the same fund. Selling an HSBC FTSE All-Share Index Fund and buying back into the same fund within 30 days triggers the rule. But: selling HSBC FTSE All-Share and buying Vanguard FTSE All-Share is NOT the same security - different fund codes, even though they track the same index. This is the "equivalent fund" workaround for genuine portfolio rebalancing.

How do I report capital gains for 2026/27?

Two routes: (1) Annual Self Assessment SA108 form - included with your 31 January return; (2) 60-day reporting for residential property disposals only - separate online process at gov.uk/report-and-pay-cgt. For shares/crypto/other assets, only annual SA reporting applies. Keep transaction records for 5 years from filing.

Can I carry forward CGT losses?

Yes - unused capital losses carry forward indefinitely against future gains. Must be claimed within 4 years of the tax year the loss arose. Once claimed and registered with HMRC, they remain available. Strategy: realise losses (without falling foul of 30-day rule) to bank them for future use - many investors crystallise losses each spring to bank them against future gains.

Does the 30-day rule affect crypto?

Yes - same-day rule + 30-day Bed & Breakfast rule + Section 104 pool all apply to crypto identically. Each token type has its own Section 104 pool. Selling BTC + buying back within 30 days triggers matching. Crypto tax software (Koinly, Recap) automatically applies these rules in CGT calculation.

Practical guide

UK CGT 30-Day Rule + Strategy 2026/27

UK Capital Gains Tax 30-day "Bed & Breakfast" rule explained, share matching mechanics, legal tax-efficient strategies including bed-and-ISA, spouse transfers, AEA timing, and 2026/27 CGT rates 18%/24%.

The 30-day Bed & Breakfast rule

UK anti-avoidance rule introduced 1998. If you sell a security and repurchase the same security within 30 days, HMRC matches the disposal against the new acquisition - NOT against your existing Section 104 pool. This prevents loss-harvesting by selling Friday and rebuying Monday.

Share matching order

Same-day rule: Match disposals against acquisitions made the same day
30-day Bed & Breakfast rule: Match against acquisitions in 30 days FOLLOWING the disposal
Section 104 pool: All remaining holdings averaged into weighted-average cost basis

Each rule applies in sequence. Same-day takes priority; if no same-day acquisitions, the 30-day rule applies; only remaining disposals match against the pool.

Legal CGT optimisation strategies

1. Bed-and-ISA (most powerful)

Sell shares from general investment account, immediately buy back the same shares INSIDE ISA. The disposal uses your £3,000 AEA. The new ISA holding grows tax-free forever - no future CGT.

Worked example: 1,000 BP shares at £4.50 cost basis, now £6.00. Gain £1,500 (within AEA):

Sell 1,000 BP at £6.00 in general account: proceeds £6,000, gain £1,500
Buy 1,000 BP at £6.00 inside ISA
Gain crystallised at £0 tax (within AEA)
New ISA cost basis: £6,000
Future BP dividends + gains in ISA: tax-free

2. Spouse transfer

Inter-spouse transfers are no-gain-no-loss. Gift shares to spouse, who then sells using their own AEA. Married couple effectively doubles AEA to £6,000/year.

3. Loss harvesting

Realise capital losses in years where you have gains. Losses offset gains, reducing CGT. Unused losses carry forward indefinitely. To avoid 30-day rule, buy equivalent-but-different fund (e.g. sell HSBC FTSE All-Share, buy Vanguard FTSE All-Share).

4. AEA scheduling

The £3,000 AEA resets each tax year. Strategic timing - sell across two tax years to use £6,000 of AEA on a larger gain.

5. Pension contribution to reduce marginal band

CGT rate depends on which Income Tax band the gain falls in. A £20,000 gain pushing you into 24% can be partly relieved by pension contribution reducing your income, moving more gain into the 18% basic-rate band.

2026/27 CGT rates

Income band	CGT rate (non-property)	CGT rate (residential property)
Basic rate band (£0-£50,270 after PA)	18%	18%
Higher/additional rate	24%	24%
Annual Exempt Amount	£3,000	£3,000

Common mistakes

Triggering 30-day rule unintentionally - selling + rebuying same fund in 30 days
Forgetting bed-and-ISA opportunity - £3,000/year of AEA wasted
Not banking losses - unused losses lost after 4 years
Missing 60-day property reporting - £100 penalty for late reporting
Confusing AEA with PA - AEA is separate from Income Tax Personal Allowance

Frequently asked questions

What is the 30-day rule in UK CGT?
The "Bed & Breakfast" anti-avoidance rule. If you sell shares + repurchase the same shares within 30 days, HMRC matches the disposal against the new acquisition (not against your existing pool). This prevents harvesting losses by selling Friday + repurchasing Monday. The rule applies to all CGT-eligible assets including crypto, ETFs and individual stocks.
How do I crystallise a gain using the AEA legally?
Use ISA wrapper or spouse transfer. Bed-and-ISA: sell shares from general account, immediately repurchase same shares inside ISA. The disposal crystallises the gain (potentially within AEA), and the new ISA holding grows tax-free forever. Spouse transfer: gift shares to spouse before they sell - uses both your AEAs. Direct sell-then-repurchase in same account triggers the 30-day rule.
What's the order of share matching for CGT?
(1) Same-day rule - match against acquisitions made the same day. (2) 30-day Bed & Breakfast rule - match against acquisitions in 30 days following disposal. (3) Section 104 pool - all remaining holdings averaged into weighted-average cost. Each rule applies in sequence - same-day takes priority, then 30-day, then pool.
Can I use bed-and-ISA to reset cost basis?
Yes. Sell shares from general account (triggers CGT), immediately buy same shares inside ISA. The disposal uses your £3,000 AEA + any allowable losses. Future gains/dividends on the ISA-held shares are tax-free. Strategy works best for shares with gain less than AEA, allowing repeated annual transfers without tax. Approximately £3,000 of gains can be sheltered per year per person.
How does spouse transfer save CGT?
Inter-spouse transfers are tax-free (treated as no-gain-no-loss). After transfer, your spouse owns the asset at your original base cost. They can then sell using their own AEA (£3,000 each). Combined, married couple shelters £6,000 of gains per year vs single AEA. Common strategy for liquidating investments before retirement.
What CGT rates apply in 2026/27?
Two rates depending on which Income Tax band the gain falls into (when added to your income): basic-rate band = 18%, higher-rate band = 24%. £3,000 AEA per individual per year. Reporting + payment via Self Assessment by 31 January following tax year end. Property disposals: 60-day reporting + payment via gov.uk/report-and-pay-cgt.
Does the 30-day rule apply to swaps between funds?
Yes if it's the same fund. Selling an HSBC FTSE All-Share Index Fund and buying back into the same fund within 30 days triggers the rule. But: selling HSBC FTSE All-Share and buying Vanguard FTSE All-Share is NOT the same security - different fund codes, even though they track the same index. This is the "equivalent fund" workaround for genuine portfolio rebalancing.
How do I report capital gains for 2026/27?
Two routes: (1) Annual Self Assessment SA108 form - included with your 31 January return; (2) 60-day reporting for residential property disposals only - separate online process at gov.uk/report-and-pay-cgt. For shares/crypto/other assets, only annual SA reporting applies. Keep transaction records for 5 years from filing.
Can I carry forward CGT losses?
Yes - unused capital losses carry forward indefinitely against future gains. Must be claimed within 4 years of the tax year the loss arose. Once claimed and registered with HMRC, they remain available. Strategy: realise losses (without falling foul of 30-day rule) to bank them for future use - many investors crystallise losses each spring to bank them against future gains.
Does the 30-day rule affect crypto?
Yes - same-day rule + 30-day Bed & Breakfast rule + Section 104 pool all apply to crypto identically. Each token type has its own Section 104 pool. Selling BTC + buying back within 30 days triggers matching. Crypto tax software (Koinly, Recap) automatically applies these rules in CGT calculation.