UK Income Tax Calculator and National Insurance Calculator 2011/12 Free UK income tax and NI calculator 2011/2012 PAYE. Compare and see if you are better off or worse off. Use this tax calculator to see if you can claim back any tax, tax refund. It is ideal for a contractor or payroll to work out tax. It is a free to use individually or commercially tax calculator tool. It is fast and calculates as you type Iknowtax.com~Site InfoWhoisTrace RouteRBL Check