ChainTax
Free tool

What did this transaction do?

Paste any transaction hash. We'll tell you which protocol it used, what assets moved, and whether it's taxable in the UK. Only have a contract address? Try the contract lookup.

For informational purposes only — not tax advice. Verify with a qualified tax adviser.

Supports Ethereum, Arbitrum, Optimism, Base, and Polygon — chain is detected automatically.

Recently explained

Real classifications from the explainer. Each one has its own permanent page.

Want yours sorted at scale? Scan your full wallet free.

How it works

1

Read

We pull the full transaction data from the blockchain — every token transfer, interaction, and internal call.

2

Sort

Our engine runs the transaction through 33 protocol-specific detectors covering Uniswap, Aave, Lido, Curve, and more.

3

Explain

You get a plain English breakdown — what happened, what it's worth in GBP, and whether HMRC considers it taxable.

Common questions about the explainer

What it does, what it doesn't, and how the classifications work.

What does a transaction hash actually tell you?
The hash is the on-chain receipt for one operation — it records every token that moved, which contract was called, the gas paid, and whether the transaction succeeded. ChainTax reads all of that and works out which protocol it was (Uniswap, Aave, Lido, a bridge, an NFT marketplace…) and what it means for UK tax.
Which chains are supported?
Ethereum, Arbitrum, Optimism, Base, and Polygon. The chain is detected automatically — paste any 0x… hash and we work out which network it belongs to. Solana, Avalanche, and BSC are not yet supported.
Is bridging taxable in the UK?
No. HMRC treats bridges, wraps (ETH ↔ WETH), and protocol deposits as transfers, not disposals — your cost basis follows the asset across the chain. ChainTax classifies these as TRANSFER so they don't inflate your CGT bill. Swaps, sales, and LP exits are different — those are disposals.
How does the GBP valuation work?
For each token in the transaction, we look up its GBP price at the exact block timestamp via a fallback chain: PriceCache → Kraken → DefiLlama → CoinGecko. USD prices are converted via the ECB FX rate for that day. If a long-tail token has no price feed, we mark the valuation as unavailable rather than guess.
Why does the explainer sometimes say "Needs review"?
33 protocol-specific detectors handle the major DeFi surface — Uniswap, Aave, Lido, Curve, GMX, Balancer, Rocket Pool, Seaport, and many more. Anything outside that surface (rare contracts, custom multisig flows, brand-new protocols) lands as Needs review rather than getting a wrong answer silently. Inside the full ChainTax product, those become a queue you can resolve manually — and your fix is preserved on every future re-sync.
Can I share an explained transaction?
Yes. Every classified transaction gets its own permanent URL at /tx/<chain>/<hash> — copy the link from the result card. The page is read-only, no login required, and includes the protocol, asset flows, GBP valuation, and UK tax note.
Does this give me a full tax report?
No — this tool explains one transaction at a time. To get a full HMRC-ready report (SA108 boxes, Section 104 cost basis, capital gains, income, loss carry-forward), you need to add your wallet to ChainTax. The free explainer is a sandbox; the paid product handles your whole tax year.
Is there a rate limit?
Yes — 10 lookups per 10 minutes per IP, to keep blockchain-data costs sustainable for a free tool. If you need to classify a high volume of transactions, that is exactly what the full ChainTax product is built for.

Want your full wallet sorted?

This tool sorts one transaction at a time. Add your wallet to ChainTax to sort everything, calculate your capital gains, and generate an HMRC-ready tax report.

Scan your wallet freeOr import from Coinbase, Binance, or Kraken

Keep reading

Reading one transaction is a start. These walk through how HMRC actually taxes the activity behind it.