Tax and tax calculator free?

i am having trouble with my tax code.i got 2 diffrent ones off the
tax office with in 6 weeks.and my problem is i was on job seekers allowance from-april 07to middle of june 07.and i started work on july 16.and since then my tax code was 522l.and the tax office said it was my correct tax code.but 6 weeks late they sent me other letter saying my tax code is 439l
i dont claim anything.i dont have a company car its my only job.
so i would be greatful for any help with this problem.and if anyone knows.any free sites were i can calculate my taxes and tax code for free.and not the tax office because every time i speak or write to then i get diffrent answers.thanks

439 is a self employed tax code i think 522L is the corect tax code which means you can earn a max of 5229 a year without paying tax (you have to ask for it back) which is an average of 拢100.50 a week you can work out if your paying the right amount of tax by taking away the hundred off your total weekly wage taking off 8% for national insurance and then anouther 17% for tax if you still have trouble you can call them at http://www.hmrc.gov.uk/contactus/helplin... and finding you office in the a-z

Have a word with your payroll department at work and ask them if they can assist. They are usually extremely helpful in this sort of situation.

Good luck!