Automatic Validation of Duplicate Purchase Ledger Invoices and Credits Merged

It would be useful if the Purchase Ledger could automatically check whether the reference input has been used before for both invoices and credits. I appreciate that it is possible to click the tick box manually to check invoices and credits but this should be an automatic check. I am aware of the Eureka add-on that auto-checks invoice references but the system should do this as standard and should also check credits as well.