It is possible for you to add a Xero Account for each of your Payment Types.
Note: This article assumes that you have already setup your Xero Accounts/Transaction Categories (as they will appear in Simple Salon for you to select). If you haven't yet setup your accounts in Xero, then you will be seeing the Xero default accounts here instead.
Go to Admin > Lists > Payment Methods.
Click Edit next to the Payment Method you would like to set a Xero Account for:
You'll notice the Xero Account (Optional) section, along with the Select button. Click Select, then a drop-down menu will generate:
Select the appropriate Xero Account for this payment method, then click Save.
Any Payment Method that is linked to a Xero Account will have an icon displayed next to it: