Substantive procedures for trade payables

Certainly reviewing after year end invoices helps. Not sure what you mean about the credit notes.

But how? Can u explain it to me?

If you receive an invoice for roof repairs on 12/1/2018, it could easily relate to work done y/e 31/12/2017 and so is an expense for y/e 31/12/2017 and needs to be an accrual at 31/12/2017. Some suppliers are quite slow at issuing invoices.

Sir, does this relate to cut off Audit as well?

Yes