What an SPL token actually is
Solana has its own native currency, SOL, which pays the cost of every transaction on the network. Tokens other than SOL are created and tracked through the Token Program, one of the programs in the Solana Program Library. Instead of each token deploying its own contract, every fungible token on Solana is managed by this one shared program — a key difference from Ethereum's model, where the token's own contract carries the logic.
Each SPL token has a "mint" account that identifies it and records details like its total supply and how many decimal places it uses. A holder does not keep tokens in their main wallet account directly; instead they own a separate token account tied to that mint — most often an associated token account, a token account derived deterministically from the owner's address and the mint. So a single Solana wallet can hold SOL plus a set of SPL tokens, each in its own token account, as distinct balances.
"SPL token" describes the format, not a specific coin. The same Token Program underlies a wide range of fungible tokens on Solana, the way ERC-20 underlies many tokens on Ethereum. When someone says "send it as an SPL token" or "USDC on Solana," they are naming the network and the token mechanism the transfer should use — and a given token, identified by its mint address, is one specific asset among many that the program manages.
What it means in a crypto payment
When a customer pays in a Solana-based stablecoin, they are sending an SPL token. The Solana versions of USDT and USDC are SPL tokens, each identified by its own mint address, so a USDT or USDC payment on Solana is an SPL token transfer settled in a Solana slot. Because every token on Solana is managed by the same program, a receiving address can accept different SPL tokens cleanly: the mint address on the transfer tells you which token arrived.
Two practical points follow. First, the same token symbol can exist on more than one chain — USDC on Solana is an SPL token, while USDC on Ethereum is an ERC-20 token. They are the same dollar of value but different on-chain objects on different networks. Second, moving an SPL token costs a network fee paid in SOL; Solana fees are typically low and confirmation is fast, which is part of why customers often choose it for stablecoin payments. The network the customer picks affects cost and speed.
SPL tokens on halfin
halfin runs a gate for Solana, covering the SOL native asset and the SPL tokens it accepts there — USDT and USDC. A payment in either stablecoin is detected as an SPL token transfer to your receiving address and credited to the same fiat-anchored balance as any other asset. halfin distinguishes one SPL token from another by its mint address, so a customer paying USDC and one paying USDT on Solana land in your ledger correctly as the assets they are.
Because invoices are fiat-anchored, accepting an SPL stablecoin does not ask you to reason about token mechanics. You bill a fiat amount; halfin maps it to the payable token figure using the live rate, locks that figure when the invoice activates, and shows the customer a concrete amount to send on Solana. Crediting is reorg-aware and waits for Solana's confirmation threshold before the invoice is marked paid. halfin supports only the SPL tokens it has gates for — currently USDT and USDC on Solana — not arbitrary tokens that exist on the network. A balance received over Solana can later be paid out, refunded, or rebalanced into another asset through balance conversion — which is asset-to-asset, not a bank withdrawal.