I have used multiple PayPal accounts on 123 Reg in the past, how do I know which one you are using?

This article refers to payments made via PayPal.

The last valid used PayPal account will be stored within your Account Management settings. This is the account that will be used for all future transactions, unless you cancel your PayPal arrangement or make a new purchase using a different PayPal account, which will then become your next active PayPal account.

To manage your payment options, please read the following Support article for more information: How do I add or update my payment details for my 123 Reg account?

Can I add multiple PayPal accounts and credit cards to help manage my 123 Reg account?

No, this is something we do not currently support. Under your Payment Priority settings, we allow up to three different payment methods to be registered, which we believe should be sufficient for all purposes.