Card checkout alongside wallet payments, with USDC on Base received by your invoice wallet.
1. Check your Coinflow account
Use Wholly Crypto 9.0.0 or later. Ask Coinflow to approve your business and enable USDC settlement on Base to per-invoice receiving addresses. Production requires customer-paid provider fees and no settlement reserves or deductions.
Availability, identity checks, limits and provider fees depend on your Coinflow account and the customer’s location. Review the final price on Coinflow before paying.
2. Connect and test in sandbox
Open Settings → Fiat payments. Save your Coinflow merchant ID, API key and Webhook Validation Key. Add the displayed callback URL in Coinflow, then check the connection. Keep credentials server-side; never share wallet keys.
The administrator sandbox checkout is a separate 10 USD test with a sandbox receiving address. It does not pay a production invoice. A successful connection check alone does not confirm business or payment eligibility.
3. Enable Base USDC in your store
Back up your project wallet and check the Base scanner. In Store → Payment methods, accept native USDC on Base and enable card payments. Use USDC, not USDbC or USDC on Ethereum. An invoice that excludes Base USDC will not offer cards.
4. Try a small live payment
After Coinflow approval, enable production and create a normal invoice manually or through the API. Choose card payment on checkout. The invoice keeps its original currency, quote and spread; Coinflow shows the customer its final fees and conversion before payment.
5. Verify receipt before fulfillment
An invoice settles only after its USDC arrives and meets your blockchain confirmation policy. A card authorization or return to checkout is not proof of payment.
Check the invoice’s Card payment details and the USDC transaction on Base. Keep your normal signed IPN or webhook fulfillment flow. Act on invoice.settled and check requires_review; never fulfill from the browser return alone. Late or conflicting payments may need review.
6. Sweep funds and handle exceptions
Keep ETH on Base for sending received USDC to your cold wallet, or configure automatic gas funding and sweeps. Handle card refunds and chargebacks in Coinflow. Never refund crypto to the provider’s transaction sender. Review disputes in Needs attention.