What is Dust?
In the language of cryptocurrencies, the term dust refers to a tiny amount of coins or tokens. An amount that is smaller than the extra fee needed for sending it becomes practically unspendable.
With Bitcoin (BTC) and other so-called UTXO-based coins, small amounts of UTXOs can accumulate (as the result of change from earlier sent payments), which, combined with higher fees, may result in a portion of balance impossible to spend.
UTXO What?
With Bitcoin (BTC) and other similar tokens (Bitcoin Cash BCH, Litecoin LTC and Dogecoin DOGE), an account balance is not just one value, but a sum of smaller values, called UTXO’s (abbreviation of unspent transaction output). Although in the wallet only the sum is visible as balance, separate UTXOs exist under the hood, and live their own life. A payment may include one, some, or all UTXOs, and as more UTXOs are included, more data is needed to describe the transaction, hence a higher fee.
Why does a Dust Error occur?
If the amount of an UTXO is smaller than the partial fee needed to send it, that UTXO cannot be sent (with current fee level). If all UTXOs are dust, nothing can be sent from the account.
For example, a Bitcoin address may contain 3 UTXOs, of the amounts: 0.0090, 0.0003, and 0.0004, for a combined balance of 0.0097. Assuming a current byte fee rate of 50 satoshis/byte, and number of bytes for one extra UTXO as 110, the extra fee for an additional UTXO is 0,0005500 (50x110 sats). This is higher than the last two UTXOs, so those are not possible to send. Only the 0.0090 UTXO can be sent – in full or partially.
What can I do?
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Do not send very small transactions with a high fee. Since the network will attempt to create a UTXO from a small transaction, the transaction will fail.
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Send what is possible using Max Amount, with default fee setting. This will leave the small UTXOs, but send out the non-dust ones.
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If nothing more can be sent with default fee setting (only dust UTXOs exist), try sending with lowered fee. You can adjust the fee from the transaction confirmation screen. Warning: with low fee a transaction will take longer, sometimes even multiple days!
How can I check my UTXOs?
Individual UTXOs are not shown in Trust Wallet (or in most other wallets), but they can be visible as an extra option in block explorers. For example, in blockchair.com here is how the list of UTXOs of an address can be listed:
Learn more here:
https://www.binance.vision/security/what-is-a-dusting-attack
https://www.coindesk.com/bitcoin-dust-tell-get-rid