How to Calculate Crypto Gains UK 2026: Complete Step Guide

Learning how to calculate crypto gains UK 2026 is essential for every UK crypto investor. HMRC treats cryptocurrency as a capital asset, meaning you must calculate crypto gains UK 2026 using the Section 104 pooling method and report any gains above the £3,000 annual CGT allowance.

Knowing how to calculate crypto gains in the UK in 2026 is no longer optional for anyone who buys, sells, or trades cryptocurrency. HMRC has made it clear that crypto is a taxable asset — and whether you made a small profit selling Bitcoin or traded hundreds of times across multiple exchanges, you are required to report any gains above the annual Capital Gains Tax allowance. This step-by-step guide covers exactly how to calculate crypto gains in the UK in 2026 — from the HMRC rules that apply to the formula you need to use, with worked examples and a free calculator built into this page.

How to Calculate Crypto Gains UK 2026 — Step by Step

This complete guide covers exactly how to calculate crypto gains UK 2026 — including the HMRC formula, Section 104 pooling rules, the same day and 30-day rules, a free calculator and a worked example. Whether you sold Bitcoin, swapped Ethereum or traded altcoins, these are the rules that apply when you calculate crypto gains UK 2026 on your Self Assessment tax return

How to Calculate Crypto Gains UK 2026 — Why It Matters

Calculating your crypto gains correctly in the UK in 2026 is about more than just paying the right amount of tax — it is about avoiding HMRC penalties for inaccurate reporting. HMRC has access to data from UK crypto exchanges and is increasingly active in investigating unreported crypto gains. Getting your numbers right from the start is significantly less painful than receiving a compliance letter later.

The good news is that once you understand the rules, working out how to calculate crypto gains in the UK in 2026 follows a straightforward formula. This guide explains it clearly, with examples.

📋 Table of Contents

1. HMRC Crypto Tax Rules UK 2026 — The Basics
2. What Counts as a Disposal?
3. The Formula — How to Calculate Crypto Gains UK 2026
4. Section 104 Pooling — How HMRC Calculates Cost Basis
5. Same Day and 30-Day Rules
6. Free Crypto Gains Calculator UK 2026
7. CGT Annual Allowance 2026
8. Worked Example — Step by Step
9. How to Report Crypto Gains to HMRC
10. Frequently Asked Questions
11. Final Thoughts

HMRC Crypto Tax Rules UK 2026 — The Basics

Before you can calculate crypto gains in the UK in 2026, you need to understand how HMRC classifies cryptocurrency. HMRC treats crypto as a capital asset — similar to shares — not as currency. This means Capital Gains Tax (CGT) applies when you dispose of cryptocurrency, not Income Tax (unless you are mining or receiving crypto as employment income).

The key rules that govern how to calculate crypto gains in the UK in 2026 are:

• CGT applies on disposal — selling, swapping, gifting, or spending crypto all count as a disposal and may trigger a taxable gain or loss
• Section 104 pooling — HMRC requires you to pool your holdings of the same coin and calculate an average cost basis
• Same day rule — if you buy and sell the same coin on the same day, those trades are matched against each other first
• 30-day rule (bed and breakfasting) — if you sell a coin and buy it back within 30 days, the repurchased coins are matched against the sale first
• Annual CGT allowance — you only pay CGT on gains above the allowance (£3,000 for 2025/26)

⚠️ Important: Swapping one cryptocurrency for another (e.g. Bitcoin for Ethereum) is treated as a disposal by HMRC. You calculate the gain or loss based on the pound sterling value at the time of the swap — not just when you eventually sell back to fiat currency.

What Counts as a Disposal in 2026?

Understanding what triggers the need to calculate crypto gains in the UK in 2026 is essential. HMRC counts the following as disposals:

• Selling cryptocurrency for pounds sterling (GBP) or any other fiat currency
• Exchanging one cryptocurrency for another (Bitcoin to Ethereum, for example)
• Using cryptocurrency to pay for goods or services
• Gifting cryptocurrency to someone other than a spouse or civil partner
• Donating cryptocurrency to charity (though this may qualify for Gift Aid relief)

The following are generally NOT disposals:

• Transferring crypto between your own wallets
• Buying cryptocurrency with fiat currency
• Holding cryptocurrency without selling or using it

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The Formula — How to Calculate Crypto Gains UK 2026

The core formula for how to calculate crypto gains in the UK in 2026 is straightforward:

📐 The Crypto Gains Formula

Gain / Loss = Disposal Proceeds − Cost Basis

Disposal Proceeds = the pound value received when you sold or swapped the crypto, minus any transaction fees on the sale

Cost Basis = the pound value you paid when you originally acquired the crypto, plus any transaction fees on the purchase

If the result is positive, you have made a gain. If it is negative, you have made a loss. Losses can be used to offset gains in the same tax year or carried forward to offset future gains — which is worth noting when you are working through how to calculate crypto gains in the UK in 2026.

Section 104 Pooling — How HMRC Calculates Cost Basis

The most important rule to understand when learning how to calculate crypto gains in the UK in 2026 is Section 104 pooling. HMRC does not allow you to pick which specific coins you sold (e.g. choosing to sell the most expensive ones to minimise gains). Instead, all coins of the same type are pooled together and an average cost per coin is calculated.

Here is how Section 104 pooling works in practice:

1. Every time you buy a coin, its cost (including fees) is added to the pool
2. The pool tracks the total number of coins and the total amount spent
3. The average cost per coin = total pool cost ÷ total coins in pool
4. When you sell, the cost basis for the disposal = average cost × number of coins sold
5. The pool is then reduced by the coins sold and their average cost

📊 Section 104 Pool Example

January 2025: Buy 1 BTC for £30,000 (+ £20 fee) → Pool: 1 BTC | Total cost: £30,020

June 2025: Buy 0.5 BTC for £20,000 (+ £15 fee) → Pool: 1.5 BTC | Total cost: £50,035

Average cost per BTC: £50,035 ÷ 1.5 = £33,357

March 2026: Sell 0.5 BTC for £32,000 (- £20 fee)

Cost basis of sale: £33,357 × 0.5 = £16,678

Proceeds: £32,000 – £20 = £31,980

Gain: £31,980 – £16,678 = £15,302

Same Day and 30-Day Rules

Two special matching rules apply before Section 104 pooling when you calculate crypto gains in the UK in 2026:

Same Day Rule

If you buy and sell the same coin on the same day, those transactions are matched against each other first — before any Section 104 pool calculation applies. This prevents investors from temporarily boosting their pool cost basis on the day of a sale.

30-Day Rule (Bed and Breakfasting)

If you sell a coin and buy it back within 30 days, the repurchased coins are matched against the sale first — again, before Section 104 pooling applies. This rule prevents investors from selling at a loss to claim tax relief and immediately buying back the same asset. When calculating crypto gains in the UK in 2026, always check whether either of these rules applies before defaulting to the Section 104 calculation.

Free Crypto Gains Calculator UK 2026

Use the calculator below to work out your crypto gains or losses quickly. Enter your buy price, sell price, quantity and transaction fees — and the calculator will show you your taxable gain and estimated CGT liability based on HMRC’s 2025/26 rules.

🧮 Crypto Gains Calculator UK 2026

Enter your trade details below to calculate your capital gain or loss and estimated CGT liability.

⚠️ Based on HMRC Section 104 pooling rules. CGT annual allowance: £3,000 (2025/26). This is a guide only — not financial or tax advice. Buy Price Per Coin (£)Sell Price Per Coin (£)Number of Coins / TokensBuy Fees (£)Sell Fees (£)Your Income Tax Band Basic Rate — 18% CGT on crypto Higher Rate — 24% CGT on crypto Calculate Gains / LossesReset

Total Cost Basis (inc. fees)—

Total Proceeds (after fees)—

Gross Gain / Loss—

CGT Annual Allowance 2025/26£3,000

Taxable Gain (after allowance)—

💰 Estimated CGT Liability

Tax Rate Applied—

Estimated Tax Owed—

Guide only. Always consult a qualified tax professional and report accurately to HMRC.

CGT Annual Allowance 2026

One of the most important numbers when you calculate crypto gains in the UK in 2026 is the Capital Gains Tax annual allowance. This is the amount of gains you can make in a tax year before you owe any CGT.

Tax Year	CGT Annual Allowance	Basic Rate CGT (Crypto)	Higher Rate CGT (Crypto)
2022/23	£12,300	10%	20%
2023/24	£6,000	10%	20%
2024/25	£3,000	18%	24%
2025/26	£3,000	18%	24%

Note that CGT rates on crypto changed in October 2024 — basic rate taxpayers now pay 18% (up from 10%) and higher rate taxpayers pay 24% (up from 20%). When you calculate crypto gains in the UK in 2026, make sure you are using the correct current rates.

Worked Example — Step by Step

📊 Complete Worked Example

Scenario: You bought 0.5 Bitcoin for £17,500 (including £25 fee) in January 2025. You sold it for £31,000 (minus £30 fee) in March 2026. You are a basic rate taxpayer.

Step 1 — Cost Basis: £17,500 + £25 = £17,525

Step 2 — Disposal Proceeds: £31,000 – £30 = £30,970

Step 3 — Gross Gain: £30,970 – £17,525 = £13,445

Step 4 — Deduct CGT Allowance: £13,445 – £3,000 = £10,445 taxable gain

Step 5 — Calculate Tax: £10,445 × 18% = £1,880.10 CGT owed

This would be reported on your Self Assessment tax return for the 2025/26 tax year (deadline 31 January 2027).

How to Report Crypto Gains to HMRC

Once you have calculated your crypto gains in the UK in 2026, you need to report them to HMRC if your gains exceed the annual allowance or your total disposal proceeds exceed four times the allowance (£12,000 in 2025/26).

Crypto gains are reported through Self Assessment — either online or by paper return. The deadline for the 2025/26 tax year is 31 January 2027 for online returns. If you have not filed a Self Assessment before, you need to register with HMRC first — ideally well before the October 5th registration deadline.

For investors with complex trading histories across multiple exchanges, a crypto tax software tool like Koinly, CoinTracker or TaxBit can automatically import your transaction history, apply HMRC rules including Section 104 pooling, and produce a ready-to-use CGT report.

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Frequently Asked Questions

How do I calculate crypto gains in the UK in 2026?

To calculate crypto gains in the UK in 2026: subtract your cost basis (purchase price plus fees) from your disposal proceeds (sale price minus fees). Apply HMRC’s Section 104 pooling rules to determine your average cost basis. Deduct the £3,000 CGT annual allowance from your total gains. Apply the relevant CGT rate — 18% for basic rate taxpayers, 24% for higher rate taxpayers.

Do I need to pay tax on crypto in the UK in 2026?

Yes — if your total crypto gains in the 2025/26 tax year exceed £3,000 (the CGT annual allowance), you must report and pay Capital Gains Tax. You must also report if your total disposal proceeds exceed £12,000, even if your gains are below the allowance. Crypto losses can be reported to offset future gains.

What is Section 104 pooling for crypto UK?

Section 104 pooling is HMRC’s required method for calculating the cost basis of cryptocurrency in the UK. All coins of the same type are pooled together, and an average cost per coin is calculated. When you sell, your cost basis is the average cost multiplied by the number of coins sold — you cannot choose which specific coins you sold.

What is the CGT allowance for crypto in the UK in 2026?

The Capital Gains Tax annual allowance for 2025/26 is £3,000. You only pay CGT on crypto gains above this amount. The allowance has reduced significantly from £12,300 in 2022/23 — it is important to use the current figure when you calculate crypto gains in the UK in 2026.

Can I offset crypto losses against gains in the UK?

Yes — crypto losses can be used to offset gains in the same tax year, reducing your total taxable gain. If your losses exceed your gains, you can carry the remaining losses forward to offset against future gains. You must report losses to HMRC to use them — they are not applied automatically.

Final Thoughts

Knowing how to calculate crypto gains in the UK in 2026 is an essential skill for any UK crypto investor. The rules are more detailed than many people expect — Section 104 pooling, the same day rule, the 30-day rule — but once you understand them, the actual calculation is straightforward. Use the free calculator above for simple transactions, keep accurate records of every trade, and consider dedicated crypto tax software if your transaction history is complex.

With HMRC increasingly focused on crypto compliance in 2026, getting your numbers right now is far less painful than dealing with an investigation later.

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Source: HMRC — Cryptoassets for Individuals

Disclaimer: This post is for informational purposes only and does not constitute financial or tax advice. Always consult a qualified tax professional for advice specific to your situation. This post contains affiliate links — we may earn a commission at no extra cost to you.