This issue is caused by the previous period's statutory return not being flagged as updated. The most common causes of this are;
Clicking no to the prompt, Do you want to update the statutory return.
A restore has taken place, which has caused the statutory return not to be updated.
To confirm the cause, you can check the statutory return copy report, which will show which periods have been updated and when.
Click Payroll, and then click Reports.
Click Payroll Reports.
Click the + icon to expand Analysis, then General.
Double-click Statutory Return (Copy).
If no report is present for the previous period, we recommend a restore to pre-period end. Where the statutory return can be processed correctly. You will then need to continue processing the payroll up to the current point in time.