How does speculation work?

How can I work out how much Tax/NI I 'Should' be deducted from my pay?

• I am currently temping and earn £10 an hour. I do 40 hour weeks with no over time. Before tax that should come to £19200 a year. Because I am temping, I get paid weekly rather than monthly. So I should be getting £400 before tax. However, where I work we have a scheme called Alternate Working Week (AWW). This means that we can work either an extra hour or two each day to accumulate an extra 8 hours and then get every second Friday off. Which is a nice perk to be honest! Anyway, this means that an average 2 weeks looks like: Week 1: 44 hours Week 2: 36 hours Instead of 40 hours x 2. So is there a way of working out how much tax I should be paying on a weekly basis? And should it make a difference in % deduction if I do take part in AWW rather then just the normal working week? At the moment and its pure speculation, I feel as though my agency might be deducting more than they should… Possibly as much as £200 over the last 4 months that I have worked with this company :( I feel this way, because last week I did a 40 hour normal week because I wanted to switch the Friday that I normally take off. Using the Calc below, I reckon I should have been paid around £322, when the reality is that I was only paid £309. Whilst £13 isn’t very much… Add that up over 4 months and it paints a different picture! I am basing this on the calculation website: http://www.i-resign.com/uk/financialcentre/tax_calculator.asp However, I think that might be inaccurate as well :P Please advise and let me know, as I will need to write up a complaint if the Agency is in the wrong as soon as possible! Kind regards and cheers in advance Rob

• Answer:

  That seems perfectly reasonable to me. However, what tax code does the agency have you on? If it is 647L then you would be fine. Tax is not worked out on a straight percentage basis (it would be so simple if it was!) but on a bracketed basis. ie Anything over a certain amount gets taxed (which would be indicated by your tax code), plus National Insurance. A more accurate website to use would be: http://listentotaxman.com/index.php Although bear in mind this does not take into consideration any in year calculations and shuold be used as guidance only.