## What is a merchant key?
A merchant key uniquely identifies your merchant to PaySimple in PMT so we move money to the correct deposit account. This key does not give access to any of PaySimple's systems, and thus it does not need to be kept secret (you may put it in client-side code).
## How will I know when a new merchant is active and ready for processing?
You can [subscribe](🔗) to the [Merchant Activated for Payment Webhook](🔗).
## What is duplicate transaction checking?
Duplicate checking is performed by the processor. It provides a means to identify duplicate transactions by the following parameters:
Same Card Number
Same Transaction Amount
Specific Transaction Category (Sale, Return, etc.)
Within a certain number of Transactions (25) in the same batch (WorldPay) OR within a certain time frame (Forte)
Same external id (Forte)
## Which card_verification_options should I choose when vaulting a card?
Card verification is a good option when you are collecting the card at a time prior to charging it.
Setting verification to `
enabled` will run an authorization that will never be charged against the card. This is the only way to verify the card is valid. `
avs_only` will verify the card postal code matches. Either option can incur a small authorization fee.
## Does the ISV Payments API support ACH payments?
Yes, if your ACH processor is Forte.
## Is there a way to update a card after it is vaulted?
Cards are immutable once created. Call the [vault endpoint](🔗) a second time to create a new token if you need to change expiration date or zip code. Then you can call the [delete endpoint](🔗) to remove the original card from the vault.
## I received a communications error when attempting a sale or credit. What should I do?
If you receive a communication error, and you set an `
external_id`, you should call [lookup by external id](🔗) with the unique `
external_id` you submitted with the request to see if the payment failed or not. If it returns a 404 or a 200 with status failed, resubmit the payment.
## Does your system send receipts to customers or must I develop this myself?
The Payments API does not send receipts to your customers. You must make sure you meet [Visa receipt requirements](🔗).