Does Interactive Brokers send my tax details to HMRC?

Account information is exchanged between tax authorities under international reporting rules, so HMRC can see that the account exists. That does not replace your return: you still have to report gains, dividends and interest yourself.

Can I use the realised P/L figure from my IBKR statement?

Not directly. IBKR's figure follows the tax lots chosen in your account, in the trading currency, while HMRC requires same-day, 30-day and section 104 matching in sterling.

Do I need SA108 if my gain is below £3,000?

Yes if your total disposal proceeds were above £50,000, or if you want to claim a loss. Otherwise gains within the annual exempt amount do not need to be reported.

Is capital gains tax included in payments on account?

No. Payments on account are based on income tax and Class 4 National Insurance, so capital gains tax is paid in full by 31 January after the tax year.

United Kingdom › Guides

Interactive Brokers UK Tax Return: SA108 & SA106 Guide

Updated: 21/10/2026

How to put your Interactive Brokers account on a UK tax return: SA108 capital gains, SA106 foreign dividends, sterling conversion and 2025/26 deadlines.

Interactive Brokers does not deduct UK tax from your gains, dividends or interest, and it does not give you a capital gains computation that follows HMRC's share matching rules. If your gains are above the £3,000 annual exempt amount, or you sold more than £50,000 of shares in the year, you report the sales yourself on the SA108 capital gains pages of your Self Assessment return, with foreign dividends and interest on the SA106 foreign pages.

Do you need a tax return for your IBKR account?

Figures here apply to 2024/25 and 2025/26. Your IBKR account belongs on a return if any of these is true:

your gains for the year, after same-year losses, are above the £3,000 annual exempt amount;
your total disposal proceeds are above £50,000, even with no gain;
you made a capital loss and want to keep it for future years;
your dividends are above £10,000, or your untaxed dividends and interest are too large to collect through your PAYE tax code.

New filers should register for Self Assessment by 5 October after the tax year ends. For 2025/26 (6 April 2025 to 5 April 2026) that date has passed, so register straight away: late registration alone does not usually bring a penalty if you file and pay by 31 January 2027.

From IBKR statement to tax return, step by step

In the IBKR Client Portal open Performance & Reports, then Statements, and run an Activity statement for 6 April 2025 to 5 April 2026.
Run statements for earlier years too if you still hold older shares, because your cost comes from the section 104 pool, not from the tax lot IBKR closed.
Convert every purchase, sale, dividend, withholding and fee to sterling at the exchange rate of its own date.
Match each sale in HMRC's order: same-day purchases, then purchases in the next 30 days, then the section 104 pool at average cost.
On SA108, under listed shares and securities, enter the number of disposals, disposal proceeds, allowable costs, gains in the year before losses, and losses in the year.
On SA106, enter gross foreign dividends, the foreign tax taken off and your Foreign Tax Credit Relief claim, plus any overseas interest.
Keep your statements and computation, as HMRC expects to see how your gains were worked out.

Dividends from UK companies held through IBKR are not foreign income: they go in the UK dividends box on the main SA100 return.

Rates for 2024/25 and 2025/26

Capital gains on shares: 18% on the part of your gain that fits into your unused basic rate band and 24% above it, for disposals from 30 October 2024. Disposals from 6 April to 29 October 2024 were taxed at 10% and 20%, so 2024/25 gains have to be split around that date.
Dividends: the first £500 is covered by the dividend allowance, then 8.75%, 33.75% or 39.35% depending on your band.
Interest: covered by the personal savings allowance (£1,000, £500 or nothing depending on your band), then taxed at your income tax rate.

Gains sit on top of your taxable income, so a large gain can push part of itself into the 24% rate even if your salary is in the basic rate band.

Worked example for 2025/26

Emma is a higher-rate taxpayer. After HMRC matching, her IBKR account shows gains of £14,000 and losses of £2,500. She also received US dividends of £1,800 gross in sterling, with £270 of US tax withheld at 15%.

On SA108 she enters £14,000 as gains before losses and £2,500 as losses. Her net gain is £11,500. After the £3,000 annual exempt amount, £8,500 is taxable, and at 24% that is £2,040.

On the dividends, £1,800 minus the £500 allowance leaves £1,300, taxed at 33.75%: £438.75. Foreign Tax Credit Relief is the lower of the US tax (£270) and the UK tax on those dividends (£438.75), so she deducts £270 and pays £168.75.

Her total for the IBKR account is £2,040 + £168.75 = £2,208.75, due by 31 January 2027.

Deadlines and penalties for 2025/26

31 October 2026: deadline for a paper return.
31 January 2027: deadline for an online return and for paying the tax.
Late filing: £100 straight away, then £10 a day after three months for up to 90 days, then further penalties of 5% of the tax due or £300, whichever is higher, at six and twelve months.
Late payment: 5% of the unpaid tax at 30 days, six months and twelve months, plus interest.

Common mistakes

Copying IBKR's realised profit and loss, which follows your account's tax lots in the trading currency, not HMRC's matching.
Converting the whole year at one average exchange rate.
Forgetting commissions and stamp duty, which are allowable costs.
Entering dividends net of US tax instead of gross.
Including shares held in an ISA, which are outside capital gains tax.
Ignoring the £50,000 proceeds test: active traders with a small net gain still have to report.

The closer you get to 31 January, the less time you have to spot a wrong pool cost or a missed 30-day match. Upload your IBKR statement to Brokers.tax and see your SA108 and SA106 figures in sterling, matched the HMRC way.