Bitcoin & money learning · Retrospective
A wallet balance has separate pieces
Draw the pieces behind a displayed balance before deciding what can be spent.
Source foundation
Ordinary Bitcoin transactions spend earlier outputs and create new outputs. Bitcoin developer guide: transactions.
A worked example
Imagine two unspent outputs of 40,000 and 70,000 satoshis. A payment needs 80,000 satoshis plus a hypothetical 1,000-satoshi fee. Using both inputs leaves 29,000 satoshis as change. Check the arithmetic: 110,000 equals 80,000 plus 29,000 plus 1,000.
Original hypothetical example. Amounts, people, events, and scenarios above are invented for learning; they are not historical observations or forecasts.
What to take from it
A balance alone does not describe the transaction that a wallet will construct.
Try it on paper
Draw a second payment that spends only the 70,000-satoshi output.
Keep the assumptions beside your answer. Check the result before applying the idea to a different situation.
Reading and limits
The linked source supports the foundation statement. The worked example and exercise are NAKAMOTO's educational analysis. This note does not establish current prices, product terms, investment suitability, or wallet compatibility.
Source reviewed 13 September 2026. For operational decisions, consult the current official documentation and the details of your own circumstances.