You can limit registrants from paying offline, but still make the ability to pay offline available on the registration by requiring them to use a password to unlock offline payments. Limiting offline payment makes it easier for the Admin, since they won't have to chase down as many registrants to submit offline payments and saves the admin time from not cashing as many checks. Adding a password on offline payments makes the registration flexible enough that in case a person doesn't have the ability to pay online they can still register using a password give by an admin.
If you haven't requested a registration already, indicate that you would like this feature added when you request a registration. If you have already requested a registration, simply let the registration expert know that you want to add password functionality to offline payments. The registration team then can use dependent functionality so that only the password question shows up if someone selects they want to pay offline. Then, only the ability to pay offline can happen if the registrants enters in the case sensitive password correctly.
When this functionality is added the workflow will be as followed:
Step 1: When the registrant selects the registration link on the Welcome Page they will see a note that says, "Online Payment in the form of Visa, MasterCard, Discover Card, and ACH Check Card Payment are all acceptable forms of payments. Additionally, you are able to pay offline by emailing the contact below for approval and by requesting a password."
Step 2: An admin would then approve or deny the offline payment request. If approved, then the admin would send a password.
Step 3: The registrant would receive the password and be able to use the password to unlock the offline payment.