Payjoin can increase the privacy of a Bitcoin payment between the payer and the payee (merchant). In case of doubt, this function should remain deactivated.
Add additional fee
The “Add additional fee (network fee) to invoice” field is about an additional fee that can be charged when an end customer sends the invoice amount into numerous instalments. The network fees for a payment are always borne by the payer. If a trader wants to forward the payment receipt later to another Bitcoin address, he must pay the network fee himself. The amount of this fee depends, among other things, on how many previous inbound transactions the new forwarding transaction is made up of. You can protect yourself from these more fees if you leave the default setting this way and only charge an additional fee if a payment is made in several instalments.
The payer will see a QR code on the payment page/checkout page for a certain period of time, through which the Bitcoin will be sent. The requested Bitcoin amount has been calculated based on the exchange rate. Since the exchange rate is very volatile and can change permanently, the exchange rate should remain valid only for a limited period of time.
It is recommended that the exchange rate is guaranteed to the customer for 15 minutes. This is a period of time that is granted by almost all traders. Accordingly, it is recommended to use the value in the field “Invoice expires if the full amount has not been paid after … minutes” to 15 minutes.
Payment invalid if transactions fails to confirm
After the payment has been made, it will take a while for the receipt to be credited to the merchant’s wallet. This may depend on how much the network fee was, which the payer was willing to pay. If the payer has paid no or only a very small network fee, a transaction may take a little longer. To protect yourself as a trader from the fact that in the meantime the Bitcoin price can fluctuate too much with “Payment invalid if transactions fails to confirm … minutes after invoice expiration” will determine how long it may take for the payment to be confirmed by the network. The default is one day (=1440 minutes).
Consider the invoice paid even if the paid amount is
When asked “Consider the invoice paid even if the paid amount is … less than expected” is about underpayments of the invoice amount. The system expects a certain Bitcoin amount. If less Satoshi actually arrives, there is an underpayment.
This can happen if the payment is not made directly from the payer’s wallet, but from an exchange or exchange office. Here, the network fee is deducted from the balance when a withdrawal is made and correspondingly less arrives.
What is to be done about this? Should the payment be rejected or is there a tolerance where you are still willing to accept the payment anyway? The default is 0 tolerance.
Consider the invoice confirmed when the payment transaction
When setting “Consider the invoice confirmed when the payment transaction…” it is a question of how much confirmation a payment was successful. There are different views of payers and merchants. For a customer (payer) the payment is executed after clicking Send in the wallet. For the merchant, the payment is not completed until it has entered Final on his wallet.
Once the customer has made the payment, this payment is immediately visible in the mempool or blockchain.
However, this transaction has not yet been confirmed by the network. Depending on the amount of network fee paid, this can be the next block after 10 minutes or may take an hour or more. There is also a theoretical risk that a sent transaction will not be confirmed at all. This would be the case if the end customer did not pay a network fee at all.
According to how many confirmations a merchant wants to make the service available to his customer depends on the product and the potential risk of fraud.
A product with a low value can already be made available with the status “ls unconfirmed”. Especially with digital accesses or downloads, the failure is more likely to be tolerated. The damage is less than dissatisfied customers who have to wait a long time for service after payment.
For products that are shipped by mail order, 1 or 2 Confirmation are responsible. Until the goods are shipped, you can check the status of the payment again.
A guaranteed receipt of payment is available after 6 confirmations, this should be used for high-priced products