How do I amend an already submitted PAYE return?

The PAYE amendment is done directly, online with the ZRA through their web site and not Harvester. However you should also amend your Harvester historic payroll data. To fix harvester values you need to go to edit payments for the respective employees and choose the exact month you want to edit. Click on the edit option and then you may edit any month for up to a year back. Once you press submit on the edit payment screen for the specific month that needs adjusting, then all the reports, like NAPSA, NHI and PAYE will be automatically adjusted. Then you can simply go to the reports link, but on the month(payroll-period) selection page, choose the "historic" month for which you would like to print or generate new returns. Then all reports will be ready for use with the adjusted values for you updated records.