I have learned that dust as very tiny amount of Bitcoin, it could be 500 or 800 Satoshi or more.
Dust limits are different by script types
- Legacy P2PKH transaction: 546 sats.
- Segwit P2WPKH transaction: 294 sats.
- Taproot P2TR transaction: 330 sats.
My question is, can custodian wallet not be able to accept such dust amount? The reason why I also ask this question is because centralized exchanges usually has a minimum deposit amount of Bitcoin but I have not observed such minimum deposit amount on custodial wallet.
Your question was answered by your sentence after that but reasons are more than just accepting or not accepting dust deposits. Centralized exchanges have to consolidate users' deposits, and move it to their other hot wallets or cold wallets. They don't want to waste own resources and money by accepting too small deposits.