PAYE Tax Calculator. Calculate your Income Tax, NI, Student Loan and Pension. PAYE Tax Calculator will calculate the amount of Income Tax, National Insurance (NI) Tax, Student Loan and Pension you should be paying for your salary. *** PAYE Tax Calculator only works for the UK tax system *** There is support for SMART (Salary Sacrifice), Employer and Private pensions. The tax results can be split into detailed tax bands by clicking on the tax summary. If you have any problems then please email support@roblovelock.com