Track capital gains on
UK shares and crypto

Import your trades to calculate gains and losses using HMRC’s same-day, 30-day and Section 104 matching rules. Track your annual exemption and prepare working papers for your tax return.

Try it Create a free account

Free to use. Trades stay in this browser until you create an account.

Gainly does not calculate tax due or submit returns to HMRC.

Gainly Home: this year’s CGT position and current Section 104 holdings

Track trades, match disposals and review gains

Import share and crypto trades

Import a CSV or add them by hand. Categories, notes, and spouse transfers.

Match disposals using HMRC rules

Same-day, 30-day bed and breakfast, then Section 104 pooling. The same identification rules for shares and cryptoassets.

Track your annual CGT exemption

See how much of the annual exemption is used and your taxable gain for each disposal’s tax year.

Simulate a sale

Explore a sale at a price you type, using your Section 104 average cost against this tax year’s gains and exemption.

How HMRC share and crypto matching works

HMRC’s share identification rules also apply to cryptoassets. Gainly applies them in order.

1
Same-day
Buys on the same day as the sale are matched first.
2
30-day
Then buys in the 30 days after the sale.
3
Section 104
Then the average-cost pool for what remains.

After matching, Gainly applies the annual exemption for the disposal’s tax year to show taxable gain.

Spouse transfers are recorded separately as no gain / no loss, with the transferred units and their cost leaving the pool.

See how HMRC matching rules are applied

A Section 104 capital gains example

You hold 200 shares with a total pool cost of £3,000: an average cost of £15 per share. You sell 50 shares for £25 each, with no fees and no purchases of the same shares on the sale date or in the next 30 days.

Sale proceeds: £1,250; 50 × £25
Allowable cost: £750; 50 × £15
Capital gain: £500; £1,250 − £750

This gain is before losses and the annual exemption. It is not tax due.

Follow the Section 104 calculation step by step

Compared with doing it yourself

Compare keeping your own spreadsheet, using Gainly and working with an accountant. You or your accountant file the return.

Compared on	Do it yourself	Gainly	Hire an accountant
Cost	No fee. It takes your time.	Free	You pay their fee
What you produce	Your own spreadsheet	A working paper: proceeds, allowable cost, gain, and taxable gain after the annual exemption	Advice, a return, and the tax due
Matching	You apply same-day, 30-day, and Section 104 yourself	Applied in that order, for shares and cryptoassets	Applied, plus judgment on cases the rules do not settle cleanly
Annual exemption	You apply the year’s exemption	Applied to the tax year of the sell date	Applied, with the rest of the return
Tax due	You work it out if you need it	Not computed	Computed and explained
Spouse transfers	You take units out with no gain	No gain / no loss. Units leave the Section 104 pool	Handled with the rest of the return
A hypothetical sale	You model it	Units × Section 104 average, this tax year only	A conversation about what to sell
Where the trades live	Your file	This browser until you create a free account	Their records
Filing the return	You file	You file. Gainly does not submit to HMRC	They can file for you

Questions about tracking UK capital gains

Does Gainly calculate the tax I owe?

No. It matches disposals and shows taxable gain after that year’s annual exemption. It does not apply CGT rates or say what you owe. See how HMRC matching rules are applied.

Will it file my Self Assessment?

No. You, or your accountant, file the return. The figures are a working paper to check first.

Does it cover crypto and shares?

Yes. HMRC’s share identification rules apply to both: same-day, then 30-day, then the Section 104 pool.

What is Section 104 pooling?

A Section 104 pool keeps the units and total allowable cost of the same asset together. Gainly uses the pool’s average cost for the part of a disposal left after same-day and 30-day matching.

How does the 30-day rule affect capital gains?

After same-day matching, a sale is matched to purchases of the same asset in the following 30 days before using the Section 104 pool. Those later purchases can change the sale’s allowable cost and gain, so keep your records up to date through that window.

What trade history do I need to import?

Include the full history that establishes each asset’s pool cost, including earlier tax years, and purchases in the 30 days after a disposal. Import buys, sells, spouse transfers and relevant fund adjustments. CSV imports use pounds sterling, with columns for action, date, asset, units and unit price; fees are optional.

Can I track gains across different UK tax years?

Yes. Import your history once, then choose a tax year to review its disposals, gains and annual exemption. The exemption follows the disposal’s tax year. Holdings show your current Section 104 pools across all years.

What records can I export for my accountant?

You can export your recorded trades as a CSV with action, date, asset, units, unit price and fee. Review matched disposals and gains in Gainly alongside those records. The CSV is a trade history, not a completed tax return or a report of tax due.

What happens to trades before I create an account?

They stay in this browser and are not sent to Gainly. Creating an account copies them into the account and clears them from the device.

What is Simulate?

A hypothetical sale at a price you type, using units × the Section 104 average, for this tax year only. It does not rematch same-day or 30-day buys.

Do I still need an accountant?

Gainly helps you review trade matching and gains. Whether you need an accountant depends on your circumstances. A tax professional can check your records, advise on transactions outside Gainly’s scope, and help with tax due and filing.

Understand your capital gains

Practical guides to the rules, with worked examples and HMRC sources.

Section 104 pooling for shares and crypto
Bought the same investment at several prices? A Section 104 pool keeps its units and allowable cost together, so you can work out the cost of a later disposal.
The 30-day rule for shares and crypto
Buying an asset back soon after selling it can change the gain on the sale. The later purchase may supply the allowable cost before your existing Section 104 pool is used.
Preparing share and crypto trade records
Reliable gains start with a complete history. Gather the transactions that establish your costs, then check them before importing or sharing records with an accountant.
Understanding capital gains and the annual exemption
The amount you receive from a sale is not the same as your gain. Follow the figures from a matched disposal through to a tax-year summary.

Start tracking your capital gains for free

Try it on this device. Create a free account when you want the trades on every browser.