Supplier payments must be unpresented in the Cashbook to be able to cancelled
The Presented checkbox on the Supplier Payments screen indicates if the payment (withdrawal) has been presented in the Cashbook.
To cancel a payment find the payment Suppliers > Payments and click on the cancel button.
Yes, as part of Suppliers end of month processing the system will automatically create a GL journal for open Sub Rental Supplier invoices. These can be posted automatically to the GL if the parameter ‘ Post Supplier Sub-Rental Accrual’ parameter is enabled.