Payment status can be accessed on your Event Dashboard by going to the Offline Payments report under Track > Reports.
If you have chosen to enable offline payment, then you will see two tabs: Not Yet Received and Received.
To notate payment, click Mark as Paid.
Please note: if you are issuing PDF tickets, they will be issued to anyone who registered whether they are paying online or offline. You will need to follow up with anyone who is paying offline to collect payment.