Answer
If you need to make corrections to an employee's payslip, you will need to navigate to the relevant pay run for which that payslip was issued.
If the pay run was in the past, you can go back to earlier pay runs in the Pays menu by clicking the Last Pay Run button on the left. You can also click and hold the Last Pay Run button for 2 seconds and then release to see a list of previous pay runs for a quick selection, or use the Jump To Pay Run Date box at the bottom of the Pays screen.
Once in the appropriate pay run, you will need to click the Edit Pay button on the right hand side to make changes to the employee's pay. If the Edit Pay screen is locked, you can unlock it by clicking the padlock icon on the bottom left. Once you've made the necessary changes, click Save + Close.
If you wish to change the metadata for a payslip (address, name, company details, etc.) that are not dollar amounts, use the Payslip Info button in the lower right of the Edit Pay window. You can also make bulk payslip info changes via Tools >> Retrospective Tool.
You can generate a new Payslip that will show the changes made by clicking the Payslips button.