It is much better to buy the OpenCart extensions with PayPal, for instant access and avoiding paperwork processing.
Credit card payment will delay the process, as they request ID to be submitted.
There is no straight forward way to upload the government issued ID in the order.
You can see that an ID is required, but there is no explanation how and where to upload.
In addition, providing personal ID documents is not recommended.

Here are the steps on how to process OpenCart payment for an extension:

Select the extensions and choose “PayPal” payment method.

2. See the difference below between paying with PayPal and Credit Card. PayPal order is available for immediate download.

3. Also, in the email confirmation sent for credit card purchase, there are NO clear instructions on where and how to upload the identification documents!