HMRC has updated its guide 'Software developers: PAYE update 23' on Income Tax and National Insurance changes from April 2019.
The update gives guidance to PAYE software developers for the 2019 to 2020 tax year. Changes to values used in technical specifications are given along with other information to help with PAYE software development.
Included are all details for Income Tax changes and Class 1 National Insurance contributions (NICs) changes from 6 April 2019.
See the guide here