Four things account for most declines. The balance may not cover the full amount including whatever the merchant adds. The billing address may be wrong — merchants check the card's address, shown on the card's page, not yours. A one-time code may be waiting: if the merchant ran a verification check, the code appears as a banner in your dashboard, and the payment fails if it is not entered. Or the merchant's category may be one the card cannot be used for. Each declined attempt also costs the card issuer's decline fee, taken from the card and listed on the pricing page. If none of those explain it, send us the merchant name and the time and we will tell you what the issuer recorded.