Coins vs tokens: why you need ETH to send USDC

It's one of the most common surprises in crypto. You have $500 of USDC on Ethereum, you try to send it, and your wallet says you don't have enough funds. Enough of what? The answer is the difference between a coin and a token — and once it clicks, a lot of wallet behaviour suddenly makes sense.

Coins are the chain's own money

Every blockchain has a native asset built into its rules. Bitcoin has BTC, Ethereum has ETH, Solana has SOL, Polygon has POL. These are coins: the network itself tracks them, and they're what the network accepts as payment for processing transactions.

When you send a coin, the chain moves it directly. There's no contract in between — just the protocol's own accounting.

Tokens live inside contracts

A token is different. On Ethereum and similar chains, a token like USDC, USDT or a governance token is a smart contract that keeps its own ledger: a list of addresses and how much of the token each one holds. On Solana, tokens follow the SPL standard, with balances held in separate token accounts.

Your "USDC balance" is really an entry in USDC's contract saying a certain amount belongs to your address. Sending USDC means asking that contract to update its ledger — moving a number from your entry to someone else's.

That's why the same token can exist on several chains as entirely separate things. USDC on Ethereum and USDC on Polygon are different contracts with different ledgers. Some versions are issued natively; others are wrapped or bridged representations of an asset held elsewhere.

Gas is always paid in the coin

Here's the part that causes the surprise. Asking a token contract to move your balance is still a transaction on the chain, and the chain charges a fee for every transaction — gas. That fee is paid in the native coin, not in the token you're sending.

So to send USDC on Ethereum, you need two things at the same address:

• the USDC you want to send, and
• a little ETH to pay for the transaction.

With no ETH, the USDC is stuck — not lost, just unable to move until you add some. The same rule applies everywhere: tokens on Polygon need POL for gas, on BNB Chain they need BNB, on Avalanche AVAX, and on Base ETH.

Solana's extra wrinkle

Solana works the same way at heart — fees are paid in SOL — with one addition. Each token you hold needs its own token account, and creating one requires a small deposit of SOL called rent. When someone sends you a token you've never held before, a token account has to be created for it. How token accounts and rent work explains the details; the short version is that you'll want a little SOL around to hold and move SPL tokens too.

Mistakes this explains

Once the coin/token split is clear, several classic problems make sense:

• "Insufficient funds" with a full token balance. You're out of the native coin for gas.
• Tokens sent to the wrong network. USDC sent on one chain doesn't appear on another, even at the same address, because it's a different contract on a different ledger.
• Sending your last coins. Emptying your ETH completely leaves any tokens at that address unable to move until you top up.
• "Free" tokens you can't sell. An unsolicited token may need gas to move — and may be designed so that trying costs you more than it's worth.

How it works in SSP

SSP shows coins and tokens per chain, inside each chain's wallet. On EVM chains, your SSP account is a smart account controlled by your 2-of-2 multisig, and gas for a token send is paid from the same vault's native coin, so keep a small amount of ETH (or POL, BNB, AVAX) alongside your tokens. When you send a token, SSP Key shows you the token transfer it decoded from the transaction — the recipient and amount of the token, not just a raw contract call.

On Solana, SSP's relay pays the network fee up front and the vault reimburses it in SOL as part of the same send, so you'll still need some SOL in the vault.

The honest summary

Coins are the chain's own money; tokens are balances inside contracts that run on the chain. Every transaction is paid for in the coin — including transactions that move tokens.

Keep a small buffer of the native coin on every chain where you hold tokens, check which network a token is on before you send or receive it, and you'll avoid the most common "where did my money go?" moments in crypto.