The price of Bitcoin and Bitcoin Cash is always changing. To prevent those price changes from hurting our customers, we require transactions to be sent within 15 minutes.
Most Bitcoin exchanges cannot send a payment that quickly. As a result, the payment can arrive late and need to be refunded. This will cost you time and money.
Many Bitcoin or Bitcoin Cash wallets do not fully support payment protocol. These non-payment protocol wallets make it too easy to send the incorrect amount or send your Bitcoin or Bitcoin Cash to the wrong place.
BitPay recommends using a Bitcoin wallet that you can trust to successfully use for Bitcoin payments. Compatible wallets can be found here.