Both our payroll systems will automatically update the tax codes when you advance your payroll to the new tax year.
A message will appear on the screen to let you know this has been done.
Alternatively, you can change them manually within the employee settings on both systems.
On QuickBooks Online Payroll click Employees in the top left corner, select the employee and then in the Tax Information section you can update the tax code.
On our PaySuite system just click on the employee's name to open the employee settings page, then click the Tax and National Insurance tab on the left. You can then update the tax code on this page.
Let me know if there is anything else I can help with. :)