CGT Bed-and-Breakfast 30-Day Calculator 2026/27
UK share matching for 2026/27: same-day rule, 30-day rule, then the Section 104 pool, with bed-and-breakfast, bed-and-spouse and bed-and-ISA examples.
When you sell shares, HMRC matches the sale first with any of the same shares you bought that day (TCGA 1992 s.105), then with any you buy in the next 30 days (s.106A(5)), and only then with your Section 104 pool (s.104). The 30-day rule stops "bed and breakfasting": selling and buying straight back to realise a gain or loss. It only matches purchases by the same person in the same capacity, which is why bed-and-spouse and bed-and-ISA work.
Worked matching scenarios
Each example assumes a Section 104 pool with an average cost of £4 a share and ignores dealing costs.
| Scenario | Matched under 30-day rule | Gain/loss on matched shares | From pool | Gain on pool shares | Total gain | Note |
|---|---|---|---|---|---|---|
| Sell 500 at £5, buy back 200 next day at £5.20 | 200 | -£40 | 300 | £300 | £260 | 200 shares matched with the repurchase under the 30-day rule; 300 from the pool |
| Bed-and-spouse: sell 1,000 at £5, spouse buys 1,000 in the market | 0 | £0 | 1,000 | £1,000 | £1,000 | The 30-day rule only matches acquisitions by the person who sold, so all 1,000 come from the pool |
| Bed-and-ISA: sell 500 at £5, buy 500 in your ISA the same day | 0 | £0 | 500 | £500 | £500 | ISA shares are held in a different capacity, so they are not matched; the gain on the sale is crystallised |
Matching rules per HMRC CG51560. The rule does not apply to a repurchase made while the person was not UK resident or was Treaty non-resident (s.106A(5A)).
Frequently asked questions
What is a Section 104 pool?
Shares of the same class in the same company that you acquire in the same capacity normally go into a single pooled holding with one average cost (TCGA 1992 s.104; HMRC CG51550). Each sale that is not matched under the same-day or 30-day rules takes shares out of the pool at that average cost. Shares matched under those rules never enter the pool.
In what order do the same-day, 30-day and pool rules match a disposal?
First with shares of the same class bought on the same day (s.105(1)), then with shares bought in the 30 days after the sale, earliest first (s.106A(5)), then with the Section 104 pool. HMRC sets out the order in CG51560.
Is bed-and-spouse a legal alternative to bed and breakfasting?
The 30-day rule only matches shares bought by the person who made the sale, so if you sell in the market and your spouse or civil partner buys the same shares in the market, your sale is matched with your pool and the gain or loss is realised. Selling the shares directly to your spouse does not do this: a transfer between spouses living together is treated as giving neither a gain nor a loss (TCGA 1992 s.58).
How does bed-and-ISA work?
You sell shares held outside an ISA and buy the same shares inside your ISA. ISA holdings are treated as held in a different capacity (ISA Regulations 1998 reg 34), so the ISA purchase is not matched with the sale under the 30-day rule: the gain or loss on the sale is realised in that tax year, and future growth inside the ISA is free of CGT. The purchase uses your ISA subscription allowance (£20,000 in 2026/27).
Do the matching rules apply to crypto?
Yes, for fungible tokens. HMRC says each type of token has its own Section 104 pool, and the same-day and 30-day rules apply in the same way as for shares (CRYPTO22200). NFTs are separately identifiable, so they are not pooled and no matching rules apply.