
If the Invoices button is missing trying to record Payments from customers via the Add Transaction screen, you need to:

Alternatively, ensure that Debtors>Setup>Update Debtors List in Transaction Entry is ticked
Note: If the Debtors toolbar icon is greyed out, this will also cause the Invoice button to disappear. Go to Setup > Settings > click on the Modules tab > tick the Activate Debtors (customers) check box