Fax Credit and Account Credit are both internal currencies that can be used to purchase certain products and services for your account. They may sound similar but these two differ primarily when it comes to the coverage or scope of their usage.
What Is Account Credit
Account Credit or Member Credit is the general internal currency that you can use to purchase, renew, and upgrade Domains, Hosting, and other Products/Services from Crazy Domains — without having to provide payment details for every transaction. You simply need to Add Credits to your Account one time, and add more whenever you need to.
Note: Your Account Credit will never expire, which means you can use it any time you need to.
Once you've successfully added Credits to your Account, you’ll see your total Account Credit available at the right-hand section of your Account Manager Home page.
What Is Fax Credit
Fax Credit is specifically intended for the Fax to Email service which lets you use your email address to send and receive faxes.
To be able to send faxes, you need to add enough Fax Credit to your account. Note that you will only be charged for sending faxes, not receiving. Once you have used up all your Fax Credits, you can just purchase additional Credits to continue sending faxes.
Fax Credit can be considered as a subset of Account Credit since you can use the latter to purchase the former. Yes, you still have the freedom to choose which Payment Option to use to reload your Fax Credit, but the quickest way is to simply use your Account Credit to pay for it.