BittyTaxFree Command-Line Crypto Tax Calculator for UK Investors

What Is BittyTax and Who Is It For?

BittyTax is a set of tools for one specific job: working out the capital gains and related figures from your cryptoasset activity under UK tax rules. It is not a portfolio dashboard or a price alert app. Its focus is the accounting step that comes at the end of the year.

The most natural users are UK-resident individuals who trade, swap or receive crypto and need a defensible record for self-assessment. Accountants and bookkeepers who handle several clients' crypto history can also use it, particularly because the output is traceable to the original transactions.

If you mainly want to watch prices or follow a long-term holding, a tracker will serve you better. BittyTax is for the moment when you need numbers you can defend.

How Cryptoasset Tax Calculations Work in Practice

Under UK rules, disposing of a cryptoasset can trigger a capital gain or loss. A disposal includes selling for pounds, swapping one token for another, or spending crypto on goods and services. The gain is roughly the value received minus the cost of what was disposed of, and the cost is usually tracked with a pooling method rather than by matching individual coins.

This is why the quality of your transaction history matters so much. Each buy, sell, fee and transfer needs a date, an amount and, where relevant, a GBP value. Missing or inconsistent records are the most common source of errors, and they are much harder to fix at the end of the tax year than during it.

BittyTax handles the arithmetic, but it still depends on the data you give it. Think of it as a precise calculator: it will do exactly what your records say, so the records must be right.

Real-World Scenarios Where BittyTax Helps

Consider someone who bought Bitcoin on one exchange, moved some to a hardware wallet, swapped part of it for Ethereum, and sent a fee in Litecoin. Each of those steps may need its own valuation. Entering them by hand is error-prone, which is where the conversion step pays off.

Another common case is a user with several wallets. The optional wallet name field lets you audit balances across them, so you can see whether the amounts you hold reconcile with the activity recorded for each account. This is useful when some coins sit on a Ledger or Trezor device and others on an exchange.

A third scenario is a user who received tokens from a DeFi activity or airdrop and wants to see how those ERC-20 transactions affect the final figures. Because BittyTax supports building its own transaction records, you can record these events consistently with the rest of your history.

Transaction Records and Why Their Format Matters

BittyTax works on a list of transaction records, each with a type. The type decides which fields are mandatory and which are optional. A buy needs an amount and a cost, while a deposit or withdrawal needs fewer details. Getting the type right is the first thing to check when a report looks odd.

Deposits and withdrawals deserve special mention. They move coins between your own accounts and are not taxable events, so they do not require a valuation. Confusing a transfer between your wallets with a sale is one of the most damaging mistakes, because it can create a gain that never happened.

When a buy, sell or fee asset is not already in pounds, the tool needs a valuation for it. You can provide a fixed value in the record, or let the price lookup supply one. Knowing which of these applies to each row saves a lot of rework.

Understanding Auditability and Why It Matters

Auditability means that every figure in your report can be traced to a source record and a documented calculation. For a tax return, this is what lets you answer a question months later with confidence. BittyTax is built with HMRC's auditing expectations in mind, so the trail from raw export to final total is kept visible.

In practice, keep the original exchange exports and the converted records together. If HMRC ever asks how you reached a number, you can show the source transactions, the valuations used and the calculation output. Retaining these files is as important as the calculation itself.

The transparency of the open-source code adds another layer: you or a qualified accountant can read how the calculations are performed rather than relying on a vendor's claim about accuracy.

Supported coins

The documentation mentions support for Bitcoin (BTC), Ethereum (ETH), Litecoin (LTC), Bitcoin Cash (BCH), XRP, BNB Chain, ERC-20 tokens, Nano and the stablecoins USDT and USDC. Hardware wallets from Ledger and Trezor are referenced as common sources of transaction data. Coverage of any specific asset depends on how its transactions are recorded in your export, so check your records against the documentation before relying on a report.