A wallet may reject a very small output even though the arithmetic of the payment seems valid. The explanation can involve dust policy: a node’s rules about outputs whose value is small relative to an estimated cost of spending them.
The Bitcoin Core review discussion of dust-policy tests explains the relationship to output type and the dust relay fee setting. This is not a fixed conversion from a market-price headline into a universal minimum payment.
Separate three questions
- Consensus: could a transaction be valid under the network’s consensus rules?
- Relay policy: will a particular node accept and forward it under its configured policies?
- Economics: would creating or later spending the output be worthwhile at the relevant fees?
These questions interact, but they are not interchangeable. A transaction being rejected by a wallet or a node does not by itself prove a consensus violation.
Read the actual rejection
Record the wallet or node version, the error message and the transaction context without publishing private keys or sensitive account information. Check the documentation for that version. Output types and policy changes can make an old numerical example unsuitable.
Do not confuse a dust threshold with a recommendation to spend every small output immediately. Fees, privacy and the wallet’s handling of change all matter. Nor should an unexpected tiny incoming amount be treated as an instruction to interact with an unknown sender.
For a learning exercise, compare documented output types and their policy calculation on a local test environment rather than sending money merely to discover the limit.
The useful takeaway is a category distinction: dust is a technical policy and cost concept. The word “small” needs a transaction structure and fee context before it becomes an explanation.