Fee-On-Transfer Tokens In Polygon Bridge Deposits Explained

Fee-On-Transfer Tokens In Polygon Bridge Deposits Explained

A transfer-tax token can deliver less to a bridge than the amount you enter. This matters when you move tokens from your own wallet: the token may charge a fee as it moves into the bridge, while the Polygon-side credit follows the amount the bridge records. For details on timing and network costs, see Polygon Bridge timing and cost; this article focuses on how token fees affect the amount.

A transfer fee changes what reaches the bridge

A fee-on-transfer token deducts some tokens whenever it is sent. It may burn them, send them to a fee address, or split the fee between both. For example, a 2% fee on a transfer of 100 tokens leaves 98 for the recipient.

That differs from a centralised exchange, which can update your account balance in its own records. With a wallet such as MetaMask, you approve an on-chain transfer: a smart contract, meaning code that runs on the blockchain, receives tokens from your address. The token’s rules apply to that transfer.

On Polygon PoS, the bridge’s Ethereum-side RootChainManager passes the deposit to a token-handling contract called a predicate. The deposit includes an amount, but the predicate’s transfer call does not by itself guarantee that the same amount arrives. What happens next depends on the token’s rules and the bridge’s accounting.

The recorded amount decides the Polygon credit

The key question is whether the bridge credits the requested amount or the amount it actually receives. A bridge designed for ordinary ERC-20 tokens, a common token standard, may use the requested amount when it records a deposit. A fee-on-transfer token can therefore create a mismatch between tokens held on Ethereum and tokens credited on Polygon.

Suppose you deposit 100 tokens with a 2% transfer fee. Your wallet may lose 100 while the bridge contract receives 98. If the bridge records and credits 100, its Polygon-side token represents more than the bridge received. A bridge that measures the balance increase could instead credit 98; one that checks for the full 100 could reject the deposit.

These are different possible outcomes, not a promise that every taxed token will bridge. A transfer can fail, or the deposit can complete with an amount different from what you expected. A token’s fee may also change, so an old successful deposit does not prove the next one will behave the same way.

A small test shows how your token behaves

Before sending a large amount, check the token’s documentation or contract for a transfer fee, tax, burn, or reflection rule. Reflection means tokens are redistributed to holders over time. Also confirm that the Ethereum token address matches the asset you intend to bridge; names and logos alone do not identify a token.

For a small test, note the amount entered, the amount that left your wallet, and the amount credited on Polygon. After the Ethereum transaction confirms, inspect its token transfers on a block explorer. Compare the transfer into the bridge contract with the recorded deposit amount, then check the Polygon credit when it arrives.

If you approve token spending first, remember that approval is separate from the deposit. An allowance is the amount your wallet lets the bridge spend; it does not change the token’s transfer fee. You still need ETH in your wallet for Ethereum transaction fees, which are separate from any tokens deducted by the transfer rule.

Choose a token that the bridge can account for

When a fee token is not clearly supported, use a standard token with no transfer tax if that suits your needs. Another option is to swap the taxed token before bridging, but the swap has its own price impact and network fee. Compare the final amount you expect to receive with what the swap and deposit transactions actually show.

Polygon Bridge is a way to move supported tokens between Ethereum and Polygon, but a token’s own transfer rules still matter. If you cannot verify how the bridge accounts for a fee-on-transfer token, do not assume the amount entered will equal the Polygon credit.

Check the token’s fee and the bridge’s recorded amount before committing a large deposit.

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