Payslip checker

Experimental - do not rely on this for anything and, preferably, do not use it all!. If you do use it, feedback is welcomed.

There are some known problems with the calculations: do not rely on this for anything!

This is aligned with UK Tax Years which run 06 April through 05 Apr

Todo list:

• Non standard NI (apprentice, youths, elderly)
• Student loans (annual total income test)
• Pensions (non sal sac tax stuff)
• Annual stuff such as savings allowances and other adjustments
• Use actual cumulative values rather than the 30/360 approximation I use
• Comprehensive testing to help with problems and errors
• Scottish Advanced tax rates and Welsh tax rates