QuickBooks Interface Error: There was an error when saving a Bill. QuickBooks error message: Only one a/r or a/p account allowed per transaction.

This error indicates that your PO Receipt Control Account in MISys is mapped to an Account Type of Accounts Payable in Quickbooks.

Resolution:

1. Navigate to the Account Set (the default Account Set is located in Company Options | Accounting Controls tab).
2. Make note of the Account Number being used for the PO Receipt Control.
3. Launch QuickBooks and navigate to the Chart of Accounts. 
4. Change the account type for this account to Other Current Liability.
5. Try processing the Invoice again.

Contact MISys Technical Support for further assistance or if the problem continues.