For detailed guidance on the procedures to follow and the reports to run please see Month End - Chapter 10 [1] [2]of the Financial Procedures Manual
It is best practice for Departments to reconcile suppliers' statements each month to ensure that they have recorded all invoices and credit notes taken. This process should be done regularly to ensure that operating results provide a true reflection of expenditure.
See this link for detailed guidance on how the Reconciliation of Suppliers' Statements [3] can be done.
Links
[1] https://www.finance.admin.cam.ac.uk/policy-and-procedures/financial-procedures/chapter-10-month-end-guidance/accounts-payable
[2] https://www.finance.admin.cam.ac.uk/policy-and-procedures/financial-procedures/chapter-10-month-end-guidance
[3] http://www.admin.cam.ac.uk/cam-only/offices/finance/procedures/nonpayexp/recsupplierstats.pdf