A lamport is the smallest unit of SOL. One SOL is 1,000,000,000 lamports, so a lamport is one billionth of a SOL. The Solana network records every balance, fee and rent deposit in lamports, and wallets and explorers convert those figures into SOL for display.
The Solana ledger does not store SOL as a decimal. Every balance, fee, rent deposit and transfer is an integer count of lamports, and the SOL figure shown in a wallet or an explorer is that integer divided by 1,000,000,000. A lamport is therefore the ninth decimal place of a SOL, and SOL amounts carry nine decimal places of precision on chain.
That is why very small SOL amounts run through every Solana transaction record. The base fee on a transaction is 5,000 lamports per signature, which displays as 0.000005 SOL. Opening a token account takes a rent-exempt deposit of about 0.002 SOL, and closing it returns the same lamports. A priority fee is priced in micro-lamports per compute unit, one millionth of a lamport, and settles as a few hundred or a few thousand lamports on top of the base fee.
An active wallet accumulates thousands of these movements a year, and the fees on failed transactions, which are still charged, add to them. That is why the SOL balance of a busy wallet drifts steadily downward between deliberate trades.
A token swap with one signature, a compute unit limit of 200,000 and a compute unit price of 10,000 micro-lamports pays a base fee of 5,000 lamports and a priority fee of 2,000 lamports, a total of 7,000 lamports or 0.000007 SOL. If the swap also creates a token account for the token received, a further 2,039,280 lamports leave the wallet as the rent deposit, and that figure comes back on the day the account is closed.
Lamports are not a separate asset. They are SOL, counted in a smaller unit, so they have no basis or holding period of their own. Every lamport amount in the record converts to SOL at 1,000,000,000 to one and joins the wallet's SOL lots, with the same basis method applied to it as to the rest.
What matters is which lamport movements are disposals and which are not. Under Notice 2014-21 SOL is property, and lamports spent on a fee are SOL disposed of under section 1001, with gain or loss measured against the basis of the lots they came from. The same lamports are a transaction cost of the trade they paid for, added to the basis of what was bought or deducted from the proceeds of what was sold. Lamports paid as a rent deposit into your own token account are not disposed of: they remain your SOL, held in a different account, and their return when the account is closed is neither a sale nor income.
Each of these amounts is negligible on its own. Across a year of Solana activity they are not. Ten thousand transactions at a few thousand lamports each is a measurable amount of SOL, every unit of it a disposal that has to be sourced from a lot, and the aggregate fee cost is a basis adjustment that moves the gain on the trades it paid for.
The reconciliation test is the SOL balance. The book's SOL position, computed in lamports, should equal the wallet's on-chain balance at any date. If it does not, movements are missing or rounded away, and the disposals and basis built on that position are wrong by the same amount.
Rounding is the failure. Many exports and import templates carry six or eight decimal places, and some drop any movement below a cent. Thousands of 5,000-lamport fee debits then vanish from the record, and the report's SOL balance climbs above the on-chain balance by their sum. The surplus never clears: when the wallet is eventually emptied, the report is left holding SOL that does not exist, and where the dust has been rounded the other way the balance goes negative and the software manufactures a zero-basis acquisition to cover it.
Read our Pros and Cons of Solana: The Future of Blockchain or a Temporary Trend? 2026 Update
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