What a memo or destination tag is.
Memo, tag, destination tag and comment are names for the same thing: a short recipient identifier sent together with the address.
Why it exists
On some networks one address belongs to many people at once, such as an exchange's deposit address. An identifier added to the transfer says whose it is. On XRP it is called a Destination tag, on Stellar, Cosmos and several other networks a memo.
Coins that require a memo
The CORE registry marks a memo as required for these coins:
- XRP (XRP Ledger): Destination tag
- XLM (Stellar): Memo
- ATOM (Cosmos Hub): Memo
- HBAR (Hedera): Memo
- KAVA (Kava): Memo
- INJ (Injective): Memo
- TIA (Celestia): Memo
- LUNA (Terra): Memo
- OSMO (Osmosis): Memo
A memo on the payout
When you receive such a coin, the exchange form asks for the memo together with the address. Take it from the same place as the address: the deposit section of your exchange or wallet. Without it the funds may not be credited.
A memo on the deposit
When you send such a coin, the deposit memo is shown on the exchange page next to the address. Put both the address and the memo in your transfer.
When a memo is optional
For every other coin the memo field in the form is optional. Fill it in only when your wallet or exchange asks for one. On TON, for example, some exchanges ask for a comment on transfers to their address.
If you forgot the memo
Do not send another deposit. Open the exchange support thread and include the transaction hash.
Getting the coins back depends on the executor and the network, and it is not always possible.