Definition. A transaction has one confirmation once it is in a block, and one more for each later block. More confirmations make it harder to remove or change.
How it works
When a miner includes a transaction in a block and the block is accepted by the network, the transaction has one confirmation. Each block added on top adds another. Blocks arrive about every ten minutes on average, though the gap between any two blocks varies a lot, from seconds to an hour or more.
To undo a confirmed transaction, an attacker would need to produce an alternative chain with more proof of work than the honest one. Section 11 of the bitcoin white paper works through the probability and shows that it falls rapidly with each additional block, for an attacker with less than half of the network's hash power.
Why it matters for a company
There is no bank to tell a company when a bitcoin payment is final. The company has to decide for itself how many confirmations it needs before it treats an incoming payment as received, releases goods or marks an invoice paid. A sensible rule scales with the amount: a small sale might be accepted after one confirmation, while a large incoming transfer might wait for several. The number should be written into the treasury policy so staff do not improvise.
The check should use a reliable view of the chain. A company running its own node, or a watch-only wallet connected to one, does not have to trust a third party's website for the confirmation count.
Confirmations also give a clean date for the books. Using the time of the block that included the transaction, or a documented alternative, keeps exchange rate conversions consistent.
Common mistakes
- Accepting zero confirmation payments for significant sums.
- Relying on a screenshot from the payer as proof.
- Using different time stamps for the same transaction in different records.
Related
Sources
Primary sources only. Each link was checked on 9 November 2026. Rules change, so confirm the current version with your adviser.
- Bitcoin developer documentationGlossary: one bitcoin equals 100,000,000 satoshis
- Satoshi NakamotoBitcoin: A Peer-to-Peer Electronic Cash System (white paper, 31 October 2008, PDF)
- Bitcoin developer documentationBlock chain guide: proof of work, difficulty every 2,016 blocks, block subsidy
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