Obtain a year end aged trade receivables report. For a sample of balances:
1 Agree the post year end payment of the constituent invoices to bank statement.
2 For unpaid amounts, agree to invoice, delivery note etc to gain assurance over existence and accuracy of the amounts receivable.
3 Consider the need to perform additional procedures to gain assurance over the valuation of the amounts receivable / consider the need for an allowance against these amounts.
Document basis for sample size and selection.