Common misunderstandings about crypto tax in Japan

Two errors point in opposite directions. One holds that a gain is taxed merely because the price rose while you held. On a personal return, an unrealised gain on a mere holding is not itself an immediate taxable event; a gain or loss is realised when a sale, exchange or payment occurs. The other holds the reverse — that nothing happens until you convert to yen. That is equally wrong, since transactions with no yen involved can still realise a gain. The two get conflated, but they are separate mistakes.

The most consequential is the belief that crypto-to-crypto swaps are untaxed. Buying ether with bitcoin, or rotating into a stablecoin, is treated as selling the asset you gave up at its value at that moment. It looks like a conversion on screen, which is exactly why it goes unrecorded — and it is the single largest reason totals fail to reconcile later.

Third is the belief that overseas exchanges or DEXs need not be reported. For a Japanese resident, income is in principle reportable regardless of where the venue sits. Whether a venue verifies identity has nothing to do with it, and on-chain records do not disappear. The absence of an operator statement simply shifts the record-keeping burden onto you.

Fourth is overlooking received income. Staking rewards, airdrops and mining rewards do not feel like transactions because nothing was bought, but the baseline framework recognises income at receipt — and a later sale produces a further gain or loss. Recording only one side leaves the calculation unreconcilable.

Finally, the belief that you can calculate per exchange and add the results. The cost basis calculation is generally per asset, combined across every place you hold it; summing annual statements does not give a correct basis. Filing on any of these misunderstandings means correcting it later, at more effort and more cost. When in doubt, check National Tax Agency guidance and consult a tax professional.