After you have created a billing group, you have the option to specify which account fees will be debited from. For tax purposes, clients may wish to have fees debited from an alternative account, so this feature will help you accomplish this. 

To update the fee location for a specific account you will navigate to Settings → Billing Settings → Billing Group.

Select the Billing Group that contains the account you wish to update. This will take you to the Billing Group Details for that specific Billing Group. All of the accounts within that group will be displayed.

Should you wish to edit the billing group's assignment, select the account you wish to change by clicking on the name of the account.

You will be presented with an option to change the fee location. The Atlas default is for accounts to be self-charged, but can be updated to either prorate across the rest of the accounts or relocate to a specific account. 

When you run the billing report, two of the included columns are fees and debits. Fees are the amounts calculated for each account, whereas debits account for fee locations and reflect any changes made here. If you do not use any fee locations, the fees and debits will be the same. 

In order to change the payment source, select Change under the Payment Source column within your billing group.

You can also pull up the Edit Group Assignment window and select the change link next to the Payment Source window.

Both of these options will pull you over to the Client Account Details where you will be able to adjust the Payment Source.