Deposits from exchanges

Once a deposit address is delegated, it has code: 0xef0100 followed by the delegate’s address. Your users keep sending to it as before, with one exception worth knowing about.

Tokens: nothing changes

A token transfer, such as USDT or USDC, calls the token contract and does not run the code of the receiving address. It arrives at a delegated address exactly as at a plain one.

Native coin: 21,040 gas instead of 21,000

A plain transfer of ETH or BNB to an address with code runs that code. The delegate accepts the coin, but running it costs a little: the transfer needs about 21,040 gas instead of the usual 21,000.

• Wallets and services that estimate the gas (eth_estimateGas), which is almost all of them, set the limit accordingly and notice nothing.
• Senders with a hard-coded limit of 21,000, which some exchanges use for withdrawals, see the transfer fail: the coin does not arrive, and the exchange marks the withdrawal as failed, or support has to sort it out.

Some exchanges may also refuse to withdraw to an address that has code at all, for tokens too.

What to do

• Delegate the addresses that receive tokens. That is where the savings are.
• If users top up an address with ETH or BNB from exchanges, do not delegate it, or keep separate deposit addresses for the native coin and for tokens.
• If an address is already delegated and receives the native coin from such exchanges, revoke its delegation.
• Ask us at support@portuna.io which exchanges are known to withdraw to delegated addresses.

Try it on a testnet

Delegate a test address in the Quickstart, then send it some test ETH twice: cast send <address> --value 0.001ether --rpc-url <RPC> --interactive arrives, while the same command with --gas-limit 21000 fails. cast estimate <address> --value 0.001ether --rpc-url <RPC> shows the gas a transfer needs.

Sweeping the native coin

You can sweep ETH or BNB through Portuna Sweep too, but it does not always pay:

• Do not delegate addresses only for the native coin. Its classic sweep needs no top-up, and a first sweep under the Glamsterdam gas rules costs about three times a plain transfer (about 66,000–68,000 gas against 21,000).
• Sweep the native coin from addresses that are delegated anyway for tokens, in batches of 10 addresses or more: then it costs 11–19% less than a plain transfer. A batch of one costs more.

How native coin sweeps are priced: Fees and tariffs.