How to Use Koinly for Your 2025/26 UK Tax Return

Crypto tax doesn’t have to be a nightmare. If you’ve got records all over the place or you’re not quite sure what HMRC needs from you, Koinly can make the whole process feel a lot more manageable. 

This guide walks through how to use Koinly to organise and prepare your crypto data for your 2025/26 tax return.

While tools like Koinly can handle the heavy lifting of calculations, the accuracy of the final figures still depends on the completeness of your data and how transactions are classified. The focus here is on getting your records into a position where they can be reviewed and used for reporting with confidence.

Contents

• 1. Why Use Koinly for UK Crypto Tax Reporting
• 2. Setting Up Your Koinly Account
  • 2.1 Portfolio Settings
  • 2.2 Cost Basis Settings
• 3. Importing Your Crypto Transactions
• 4. Reviewing and Categorising Transactions
• 5. Generating HMRC-Compliant Tax Reports
• 6. Filing Your Self Assessment
• Conclusion
• FAQs

1. Why Use Koinly for UK Crypto Tax Reporting

Filing a Self Assessment tax return with crypto activity can feel overwhelming. Between share pooling rules, same-day and 30-day matching, income from staking, and hundreds of transactions across wallets and exchanges, it is nigh on impossible to keep track of everything manually.

This is where crypto tax tools come into their own. For example, Koinly is built with UK tax rules in mind and, providing it has access to your full trading history, produces reports in a format that is ready to use for filing.

Here's how Koinly helps UK investors with their transaction tracking and reporting:

• Share pooling: Calculates gains using HMRC's share pooling method, incorporating same-day and 30-day rules.
• Income categorisation: Distinguishes between capital gains and income from activities like staking or airdrops.
• HMRC-compliant reports: Generates reports that align with HMRC requirements, simplifying the Self Assessment process.

Koinly is a powerful calculation tool, but it does not determine the correct tax treatment in every scenario. It reflects the data and categorisation you provide, which is why review remains an essential part of the process.

2. Setting Up Your Koinly Account

Firstly, sign up at Koinly.io and select the United Kingdom as your country. Before diving into your transactions, it's important to ensure the right settings are selected for UK tax rules.

2.1 Portfolio Settings:

In Settings > Portfolio, review the following settings:

1. Set your base currency to GBP.
2. Set the beginning of the tax reporting year to 6th April.
3. Tick to treat the following as Income: Mining and Rewards.
4. Tick whether or not airdrops should be treated as income (see note below)

If you usually receive airdrops, you need to consider whether they should be treated as income or not. Generally, if you had to do some kind of activity to receive the airdrop, it is treated as income, but if the airdrops were received without expectation, then they are not treated as income. In the screenshot below, the setting is left unticked, which reflects a scenario where airdrops were received without expectation - but your own treatment should reflect your specific circumstances.

2.2 Cost Basis Settings

In Settings > Cost Basis, review the following settings:

1. Ensure that "Cost Basis Method" is set to "Shared Pool / Individuals".

3. Importing Your Crypto Transactions

To get accurate tax calculations, Koinly needs your entire transaction history, not just the activity from this tax year. That’s because HMRC’s share pooling rules are based on cumulative acquisition data. If anything is missing, your gain or loss figures will likely be incorrect.

You should import all crypto transactions from every exchange, wallet and blockchain you’ve used.

Koinly supports over 800 platforms, and you can import data in three ways:

• API integration: This is the most reliable method. Koinly automatically syncs your past and future transactions.

• CSV upload: Useful if a platform does not offer API access or if you want to cross-check the data.

• Manual entry: Best for wallets, older records or unsupported platforms.

Be sure to select the full transaction history option where possible. Missing even a single transfer or buy order from a prior year can throw off the cost basis and distort your gains or allowable losses.

Once all your data is imported, Koinly will merge it into one unified transaction list, ready for reconciliation.

4. Reviewing and Categorising Transactions

This is the stage where most issues arise in practice. Koinly can import and label transactions automatically, but it cannot always interpret the underlying activity correctly, especially where DeFi, bridging or complex transaction chains are involved.

Once you’ve imported all your transactions, it’s time to review and tidy up the data. Koinly attempts to categorise transactions, but there will often be transactions that need manual input from you:

• Identify errors: Koinly flags potential issues for your attention - use the "Warning" filter to review these.
• Categorise income: Label transactions correctly (e.g., staking rewards, airdrops).
• Match transfers: Ensure internal transfers between your wallets are correctly identified to avoid misreporting.

Resolving warnings is important because incomplete data can affect both your calculations and reporting obligations. Learn more about the hidden costs and risks of DIY crypto tax.

You should also review Koinly’s categorisation more generally to ensure it correctly reflects the nature of the transaction. Here are some resources to help you with correctly categorising different crypto transactions:

• Mining
• Staking
• Airdrops
• Gifting
• NFTs

The above list is by no means exhaustive, therefore you should consider wider research if you are involved in other types of crypto activity.

If your activity includes DeFi protocols, bridging, wrapped tokens, liquidity pools, or high-volume trading, manual review becomes even more important. Automated categorisation is a starting point, not a substitute for judgement. The more complex the activity, the more important it is to sense-check the outputs before relying on them for filing.

When reviewing the categorisation of transactions, it can be helpful to filter the transactions by coin type. For example, in the screenshot below, we are reviewing all transactions for NuCypher, which in this scenario the investor never traded and only ever received as Rewards for completing tasks on Coinbase (i.e. it is considered income). The default tag applied by Koinly is "Deposit", but the tags for all NuCypher transactions have been changed to “Reward” in one go due to the filter.

At this point, your data should be organised, but not assumed to be correct. The purpose of this stage is to reduce errors and highlight areas that may require further review before relying on the outputs.

5. Generating HMRC-Compliant Tax Reports

Once your transactions are fully imported and reviewed, you're ready to generate your tax reports.

Go to the ‘Tax Reports’ section and select the 2025/26 tax year. Koinly will offer  several downloadable reports based on your data, which can be seen in the screenshot below..

The reports you need will depend on the nature of your crypto activity, but these are the most commonly used for UK Self Assessment:

• Complete Tax Report: A full summary covering income, expenses, capital gains and end-of-year balances. This is useful for your records or sharing with an accountant.

• Capital Gains Report: Shows disposals, gains, losses and allowable costs. You’ll need this to complete the SA108 section of your tax return.

• Income Report: Summarises staking rewards, airdrops, mining income and other crypto earnings treated as income rather than capital gains.

These reports form the basis of your tax return, but they should be sense-checked before filing. Unexpected gains or losses often indicate missing data, incorrect categorisation, or unmatched transfers rather than genuine tax outcomes.

6. Filing Your Self Assessment

Once your reports are complete and you are comfortable that the underlying data is complete and accurate, you can proceed to complete your Self Assessment.

• Log in to your HMRC online account.

• When filling in the SA100, make sure you tick the box to indicate that you had capital gains during the year.

• Use the figures from your Koinly Capital Gains Report to complete the SA108 form. This includes your total disposals, gains, losses, and any allowable costs.

• If you received staking rewards, airdrops or mining income, include those in the ‘Other Income’ section (unless you are considered to be "trading", in which case complete the Self-Employment section). Remember to consider whether you can claim the Trading Allowance against this income.

• Submit your Self Assessment by 31 January 2027 to avoid penalties.

If there are any areas of uncertainty, it is generally better to resolve them before filing rather than retrospectively correcting errors.

Conclusion

Koinly is a powerful tool for bringing together fragmented crypto records and producing structured reports. For many investors, it is the first step towards understanding their tax position.

However, in practice, the most common issues we see do not come from the calculations themselves, but from incomplete data, incorrect categorisation, or misunderstood transactions.

By using Koinly to organise your records, you are putting yourself in a much stronger position, whether you choose to file yourself or seek support.

In practice, the key step is making sure those figures stand up to review.

Most clients who come to us already use tools like Koinly. The challenge is rarely generating the reports, but ensuring they reflect the correct tax position.

If you want confidence that your Koinly reports are complete and correctly treated before submission, our our crypto tax support packages include detailed reviews of your transactions and are designed to ensure your figures are robust before for filing.

FAQs