Enter every purchase and sale of one holding, oldest first. This works out the pooled average cost HMRC uses, and the gain on each disposal — which is usually not the gain people expect.
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| Type | Units | Price each (£) | Fees (£) |
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Add a buy to begin.
For UK capital gains tax, shares of the same class in the same company are treated as one pool — a Section 104 holding. Every purchase adds to both the number of units and the total cost. When you sell, your cost basis is the pooled average, in proportion to what you sold. You cannot choose to have sold the cheap ones.
The classic surprise. Buy 100 at £10, then 100 at £20. The pool is 200 units costing £3,000 — £15 each. Sell 100 at £25 and instinct says you made £1,500 on the cheap batch. The pooled cost says £1,000, because the cost that came out of the pool was 100 × £15.
Dealing fees on a purchase are added to the pool cost. Fees on a sale are deducted from the proceeds. Both are treated as allowable costs here.
For a real disposal of any size, HMRC's helpsheet HS284 is the reference, and an accountant is worth the fee.
The reason most people meet pooling at the worst moment is that the pool is only reconstructed at the point of sale, from years of contract notes. OwnWorth keeps it as you go, so the unrealised gain sitting inside a holding is visible before you decide to sell anything — how that works.
See it with an example portfolio Joint property equity calculator →
OwnWorth is a record-keeping and planning tool, not financial, legal or tax advice, and we are not regulated to give any. Figures you enter are your own; projections are estimates based on them.