Supported Payment Methods

Copy page

Authorization Methods

Method	x402 V2 scheme	Description	Token support
eip3009	exact	Native transferWithAuthorization; no prior approval	U and USD1
permit2-exact	exact	Permit2 authorization for one exact transfer amount	Any configured ERC-20
permit2-upto	upto	Permit2 authorization for an upper bound; settle a smaller amount	Any configured ERC-20

permit2-exact and permit2-upto require the payer to grant a one-time ERC-20 allowance to the canonical Permit2 contract. The payer then signs a new EIP-712 authorization for each payment; no additional approval transaction is needed while sufficient allowance remains.

eip3009 requires no approval transaction because supported tokens implement transferWithAuthorization directly.

Supported Networks

Network	CAIP-2 ID	Chain ID	Usage
BNB Smart Chain Mainnet	eip155:56	56	Production
BNB Smart Chain Testnet	eip155:97	97	QA only

Production Assets

Token	Contract address	Decimals	EIP-3009	Permit2
U	0xcE24439F2D9C6a2289F741120FE202248B666666	18	Yes	Yes
USD1	0x8d0D000Ee44948FC98c9B98A4FA4921476f08B0d	18	Yes	Yes
USDC	0x8AC76a51cc950d9822D68b83fE1Ad97B32Cd580d	18	No	Yes
USDT	0x55d398326f99059fF775485246999027B3197955	18	No	Yes

Amount Encoding

All amounts are unsigned decimal strings in the token's smallest unit. Do not send human-readable decimal values.

For an 18-decimal token:

• 1 token = "1000000000000000000"
• 0.01 token = "10000000000000000"

Read decimals() from the asset contract or trusted token metadata before encoding an amount. Use integer arithmetic; never use floating-point numbers for token values.

Permit2 Contract

The canonical Permit2 contract on BSC mainnet and testnet is:

Code
0x000000000022D473030F116dDEE9F6B43aC78BA3

This is the contract the payer approves. It is not the same as the B402 Permit2 proxy address placed in permit2Authorization.spender; obtain that proxy from kinds[].extra.spenderAddress.

See Permit2 Signing for the typed-data fields and witness rules.