A Bed and ISA sale triggers capital gains tax on the disposal, but only the portion of your gain above the £3,000 annual exempt amount is charged. For the 2025/26 tax year, the rate is 18% if the taxable gain sits within your basic-rate income band and 24% on any part that falls in the higher-rate band.1GOV.UK. Capital Gains Tax: What You Pay It On, Rates and Allowances The rebuy inside the ISA is not itself a taxable event, but the whole transfer is capped by the £20,000 annual ISA subscription limit.2GOV.UK. Individual Savings Accounts (ISAs)
Why the Sale Is a Disposal
When you sell shares from an ordinary taxable account, HMRC treats it as a disposal for capital gains tax purposes regardless of what you do with the proceeds. Buying the same shares back inside a stocks and shares ISA does not change that. ISA rules require subscriptions to be made in cash, so shares held outside an ISA cannot simply be moved across; you sell, the cash lands, and you repurchase inside the wrapper.3GOV.UK. How to Manage ISA Subscriptions for Your Investors The narrow exceptions involve employer share schemes such as Save As You Earn options and Share Incentive Plans.
The gain is worked out by subtracting the original purchase price, plus dealing costs from that original buy, from the sale proceeds. A positive figure is a chargeable gain. A negative figure is a realised loss, which is useful in its own right (see below).
The Annual Exempt Amount and the 2025/26 Rates
The first £3,000 of net gains across all your disposals in the tax year owes no tax. That threshold has been frozen since 2024/25, down from £12,300 two years earlier. Anything above £3,000 is taxed at rates that depend on where the gain sits once added to your taxable income:
- 18% on the portion of the gain that falls within the basic-rate income band
- 24% on any portion that pushes into the higher-rate band
These rates apply to shares and most other chargeable assets from 6 April 2025.1GOV.UK. Capital Gains Tax: What You Pay It On, Rates and Allowances If you’re holding substantial unrealised gains in a taxable account, spreading a Bed and ISA over several tax years lets you use each year’s £3,000 exempt amount, rather than crystallising a single large gain in one year.
Using Losses to Cut the Bill
Bed and ISA is worth considering even when a holding is down. Selling a loss-making position crystallises the loss, which can be set against gains in the same tax year and reduce what you owe. Unused losses can be carried forward indefinitely, provided you report them to HMRC within four years of the end of the tax year in which they arose.
One rule to keep in mind: you must use the annual exempt amount before applying carried-forward losses. You cannot preserve the exempt amount by drawing down losses first. If net gains for the year are already below £3,000, carried-forward losses aren’t touched, which is the efficient outcome anyway.
Why the 30-Day Matching Rule Doesn’t Block This
Section 106A of the Taxation of Chargeable Gains Act 1992 introduced a 30-day share matching rule: if you sell shares and buy the same security back within 30 days in a normal taxable account, the disposal is matched to the new purchase rather than to your original cost, so the cost basis doesn’t reset.4legislation.gov.uk. Taxation of Chargeable Gains Act 1992 – Section 106A
A Bed and ISA sits outside that trap because the repurchased shares land inside an ISA, a separate legal wrapper exempt from capital gains tax. HMRC treats the sale as a genuine disposal for CGT even though the same shares are bought back the same day. The matching rule does not interfere, and future gains and dividends on the shares now held in the ISA are outside CGT altogether. That is the whole point of the strategy.
The £20,000 Ceiling on How Much You Can Move
The annual ISA subscription limit is £20,000 for the 2025/26 and 2026/27 tax years, and it is shared across all ISA types you hold: cash, stocks and shares, innovative finance, and Lifetime ISA.2GOV.UK. Individual Savings Accounts (ISAs) If £8,000 has already gone into a cash ISA this tax year, only £12,000 of headroom remains for a Bed and ISA. Over-subscribing can lead HMRC to void the tax-exempt status on the excess, so check your remaining allowance before executing. The tax year runs 6 April to 5 April.
For a large taxable portfolio, the £20,000 cap means a full transfer can take several years. Each year’s exempt amount can be paired with the year’s subscription allowance to move a slice at a time.
Other Costs That Affect the True Tax Position
The CGT figure is not the only cost eating into the transfer. Three others matter when working out whether a particular Bed and ISA is worth doing this year:
- Stamp Duty Reserve Tax at 0.5% on the electronic repurchase of UK shares, collected automatically on the buy side.5GOV.UK. Tax When You Buy Shares
- Dealing charges. Some platforms bill both legs; others only the rebuy; a few bundle the pair into a single Bed and ISA fee.
- The bid-offer spread. You sell at the bid and buy back at the higher offer, so you’ll usually end up with slightly fewer shares in the ISA than you held outside it. Small on liquid FTSE 100 stocks, larger on thinly traded names.
For a holding where the unrealised gain is small relative to these frictions, the transfer may not be worth doing in that particular year. For long-held positions with substantial gains, the future CGT saved on growth inside the ISA typically outweighs the one-off costs.
Reporting the Gain to HMRC
Two thresholds decide whether you need to file. If your total disposal proceeds across all sales in the tax year exceed £50,000, you must complete the capital gains pages of your self-assessment return even if net gains are below £3,000. Below that proceeds threshold, you only need to report when there is tax to pay on gains above the exempt amount.
Taxable gains go on the capital gains summary (SA108) as part of self-assessment.6GOV.UK. Self Assessment: Capital Gains Summary (SA108) You’ll need the original purchase date and price, the sale date, the sale proceeds, and any allowable costs, so keep contract notes from both the original buy and the Bed and ISA sale. The deadline for online returns is 31 January after the tax year ends. Gains realised in 2025/26 (year ending 5 April 2026) must be reported by 31 January 2027.7GOV.UK. Self Assessment Tax Returns: Deadlines
Late payment of CGT attracts a 5% surcharge after 30 days, with further 5% penalties at six and twelve months. Errors in returns can trigger penalties of up to 100% of the lost revenue if HMRC judges the mistake careless or deliberate. Where the gain sits within the exempt amount and proceeds are below the reporting trigger, the paperwork is minimal; where it doesn’t, the filing obligation is not optional.