The 30-day rule, counted and priced.

Sell to realise a loss, rebuy within 30 days, and the bed and breakfast rule matches your sale against the rebuy instead of your pool, and the loss you planned largely disappears. Two questions decide every harvest, when can I rebuy, and what happens if I do not wait. Both answered here, on this page, nothing sent anywhere.

When can I rebuy?
day 0
The window

One date and the whole window is counted, from the browser's own clock.

  • The date you sold, or plan to sell

The statute matches acquisitions in the 30 days after the disposal, so the first clear day is day 31. Same-day rebuys are matched too, under a separate rule. Counted in your browser against your own clock, nothing transmitted.

What happens if I rebuy early?
section 104
The matching

The pooled result needs three figures. The rebuy then shows you what survives.

    Matched in statutory order, same day under section 105 first, then the following 30 days under section 106A, then whatever is left against your section 104 pool. Fees left out for clarity, they change the figures a little, never the shape. Coins rebought beyond the quantity sold simply join your pool at the rebuy price.

    Once you know what the matching leaves you, the capital gains tax calculator prices the year it lands in.

    Your real windows, from your real history.

    This page prices one trade you type in. The app's harvesting view reads your actual records and counts every open 30-day window you have, per asset, down to its first clear day, alongside the losses worth harvesting and a warning when a harvest would be wasted under the £3,000 allowance. On your machine, free up to 1,000 transactions.

    Open the harvesting view

    Quick questions.

    How long do I have to wait before buying back?
    Thirty-one days. The rule matches your disposal against anything you buy in the 30 days after it, so sell on 13 August and the first rebuy day that leaves your pooled loss intact is 13 September. The date calculator above counts it for any sale date.
    What actually happens if I rebuy inside the window?
    Your sale is matched against the rebuy instead of your section 104 pool. Your result becomes the difference between the sale price and the rebuy price, usually a small number, and the pooled loss you were trying to realise does not happen. The pool sits where it was.
    Does buying a different coin restart the clock?
    No. The rule matches per asset. Sell ETH and buy BTC the same afternoon and no matching occurs, you have simply swapped exposure. Rebuying the same asset is what triggers it, and a crypto-to-crypto swap back into the sold asset counts as a rebuy.
    What if I rebuy fewer coins than I sold?
    Only the rebought quantity is matched against the rebuy. The rest of your disposal matches your pool as normal, so a partial rebuy realises part of the pooled loss. The calculator splits the two parts and shows each.
    What happens if I rebuy on the same day I sell?
    A different rule bites first. Section 105 matches a disposal against acquisitions made on the same day before the 30-day rule of section 106A is reached at all. Same-day quantity is matched first, then anything bought in the following 30 days, then whatever is left runs against your section 104 pool. The matching calculator handles all three in that order.
    Does the rule apply to gains too?
    Yes, matching is mechanical, it does not care which direction the number points. Sell high and rebuy lower within 30 days and the matched gain can be larger than the pooled gain would have been. The rule is symmetric, the planning around it usually is not.
    Is this calculator sending my figures anywhere?
    No. It runs entirely on this page in your browser, nothing you type is transmitted or stored anywhere. The copy link button puts your figures in the fragment, the part of a URL after the # symbol, which browsers never send to any server.

    The 30-day rule, section 106A TCGA 1992, same-day matching, section 105, the pool itself, section 104, applied to crypto through HMRC's CRYPTO22200, accessed 25 August 2026. General information, not personal tax advice.