Capturing self-custody wallet activity

Start with an inventory of addresses. Even if you think of yourself as using one wallet app, a hardware wallet can hold several accounts, and one seed generates addresses across several chains. Any app you used previously counts too. Build the list of addresses you can say are yours first — if it is incomplete, everything downstream is incomplete.

With the list in hand, export history per chain from the relevant explorer. Most offer a CSV export for an address. When you do, check that the export covers token movements and contract interactions and not only plain transfers; these are often on a separate tab that the default view does not show.

What comes back is a list of 'this much of this moved from this address to that one'. From there you separate movements between your own accounts — a withdrawal from an exchange to your wallet, a transfer between two of your wallets — from real transactions with others: sending, receiving, swapping, collecting rewards. With your address list you can sort these mechanically by whether the counterparty address is yours. That is precisely why the list comes first.

Gas costs need judgement. Every transfer or interaction burns some native token, and how that is treated depends on what the spending relates to rather than following one rule. Failed transactions consume gas too. Since the volume adds up, at minimum keep the data — when, on which chain, how much — and confirm the treatment with a tax accountant.

Where you interacted with DeFi contracts, the explorer view alone may not tell you what happened: one action can move several tokens, and a token you received may function as a receipt for a deposit. If you cannot describe what the action was, you cannot classify it correctly. This is where a note written at the time earns its keep. The treatment in this area is not always clearly established, so read tax-defi-swap and consult a professional.