The single decision that shapes crypto tax treatment is whether a jurisdiction classifies these assets as currency or as property. Most chose property, and everything else follows from that.
Property classification makes swaps taxable
Spending a currency is not a disposal of anything. Disposing of property is, and a gain or loss is calculated against what was originally paid.
Under property treatment, exchanging one token for another is a disposal of the first, even though no conventional money was involved at any point.
This surprises users who think of trading as one continuous position, and it is the most common source of unexpected liability.
Cost basis needs a consistent method
Calculating a gain requires knowing what a particular unit cost, and units bought at different times are indistinguishable once pooled.
Jurisdictions specify a method, whether first in first out, an averaged pool, or specific identification where individual units can be tracked.
Applying different methods to the same history produces different results, so consistency across years generally matters as much as the choice itself.
Income and capital treatment differ
Assets received as staking rewards, mining output or airdrops are typically treated as income valued when received, not as a purchase at zero cost.
That receipt value then becomes the cost basis, so a later sale produces a separate gain or loss measured from it.
Two events therefore arise from one asset, and the first can create a liability in a year when nothing was sold and no cash was received.
Record keeping is the practical burden
Every transaction needs a date, a value in local currency at that moment, the fee paid, and a link to the disposal it eventually pairs with.
Exchanges provide partial histories, on-chain activity provides another part, and accounts that have since closed provide none.
Reconstructing years of activity retrospectively is considerably harder than recording it as it happens, which is the one durable piece of general guidance here.
Rules vary and continue to change
Treatment of lending, liquidity provision, wrapped assets and cross-chain transfers is unsettled in many places, and positions have shifted repeatedly.
Reporting obligations placed on exchanges are also expanding, which changes what authorities can see independently of what a taxpayer files.
Specifics differ by jurisdiction and change over time, and anyone with material activity needs advice from a professional familiar with their own country's rules.