You can work out on the tax code using employee's P45 or the HMRC's 'Starter Checklist' (which replaced the P46) provided by the new employee. The link below will take you the HMRC web page wherein you can work out on the tax code and find all the related information.

HMRC link : https://www.gov.uk/new-employee-tax-code

Once you obtain the tax code, you can record it in our payroll application.