As a part of a recent audit, a summary of the audit team’s planning meeting

As a part of a recent audit, a summary of the audit team’s planning meeting identified the following specific risks.
Employee benefits expense
The superannuation rate changed on 1 July 2021. Due to a lack of controls and processes around payroll, there is a risk that the employee benefits expense is calculated on an expired superannuation rate.
Trade receivables
There is a risk that there are long-outstanding debts within this balance that are not recoverable.
Trade payables
There is a risk that the trade payables amount has been understated.
For each of the three financial line item above, determine the key assertion at risk and design a substantive test of details to address each assertion at risk.