How crypto cards work.

The 30-second answer

1. You fund the card with crypto (or sometimes fiat) at the issuer.
2. You tap the card at a merchant.
3. The issuer converts your crypto to fiat at point of sale, settles the merchant in local currency.
4. You see the spend as a crypto debit on your wallet/account.

That is the whole flow. Everything else is detail.

The settlement architecture

Every crypto card has the same fundamental architecture, with one variable: where your unspent crypto lives.

Custodial cards (RedotPay, Crypto.com Visa, Bybit Card, Nexo Card): the issuer holds your unspent crypto in a custodial wallet. At point of sale, the issuer's custody platform converts to fiat and pays the merchant.

Self-custody cards (MetaMask Card, Gnosis Pay, COCA): your unspent crypto stays in a wallet you control. At point of sale, an on-chain transaction fires (settlement contract or direct Safe spend); the issuer's partner settles the merchant in fiat. Funds never sit in a custodial pool.

MPC cards (Bleap): private key split between you, the issuer, and a third co-signer. No single party can move funds unilaterally. The middle ground between custodial and self-custody.

See custodial vs self-custody for the deeper architectural comparison.

What the merchant sees

Nothing unusual. The merchant terminal sees a standard Visa or Mastercard authorisation. They get paid in their local currency by the issuer's bank partner. They do not know you funded the card with bitcoin instead of euros. From their perspective there is no difference; this is why crypto cards work everywhere Visa or Mastercard work.

The fee layers

1. Conversion fee: the spread between the issuer's crypto-to-fiat rate and the market mid-price. Typically 0.5-2.5% on spend.
2. FX fee: additional spread when your spend currency differs from the card's base currency. Typically 0-3%.
3. Network fees on top-up: gas costs on the blockchain when you fund the card. Tron USDT: ~$1-2. Ethereum USDC: $5-30 depending on congestion. Polygon: pennies.
4. ATM fees: separate fee structure for cash withdrawals (typically higher than spend). See ATM fees guide.

Full breakdown at crypto card fees explained.

KYC, what it actually requires

Every crypto card requires KYC (Know Your Customer) at signup. Visa and Mastercard rails require identification under FATF Travel Rule and EU AMLD obligations. Standard documents:

• Government photo ID (passport, national ID, driver licence)
• Selfie / liveness check (matches you to your ID)
• Proof of address (utility bill or bank statement within 3 months)

No reputable crypto card is "no KYC" in 2026. See the truth about no-KYC crypto cards.

The lifecycle of a single spend

Let's trace a real $50 coffee purchase in Lisbon paid with a custodial card funded from USDC:

1. Tap. Card emits a Visa authorisation for €47 (the EUR equivalent of $50).
2. Issuer authorises. Issuer checks your card balance is sufficient; sends approval.
3. Conversion. Issuer converts $50.50 of your USDC to €47.00 (1% conversion + 1% FX = $50.50 cost, $47 to merchant).
4. Merchant settles. The merchant's bank receives €47 within standard Visa settlement timeframes (typically 1-3 days).
5. Your balance updates. USDC balance debited $50.50; transaction appears in the app.

For a self-custody card, replace step 3 with an on-chain transaction that mints $50.50 of stablecoin from your wallet and routes it through the settlement contract.

Why this matters

Three practical implications follow from understanding the architecture:

1. Crypto card spend is a tax disposal. Most jurisdictions treat the conversion as a sale of crypto, which is a CGT event. See crypto card tax by country.
2. Custody matters for solvency risk. Custodial cards expose you to issuer-failure risk on your unspent balance. Self-custody cards do not.
3. Fees compound. The 1-3% spread on every spend adds up. Use the right card for the right spend type to minimise the bleed.