Information/Website(s) on how to make a employee tax calculator

Hi.

Been working on a payroll system for a while now for a college project..Finally got to the stage of calculating the tax for the staff (Which is rather important lol)

I'm VERY new to VB and this project doesn't have to be perfect...if i'm honest i think all the database side of it is wrong...however it works(ish)

Math isn't my strong point so iv very confused about Tax etc.

So far i have wrote a code which works...

txtTotal.Text = Val(txtHours.Text) * Val(txtPay.Text) * 4
decIncome = Convert.ToDecimal(txtTotal.Text)
decDeductions = decIncome * 0.22
decAmount = decIncome - decDeductions

txtTotal.Text = decIncome
txtTax.Text = decDeductions
txtNetpay.Text = decAmount


I know i have 22% as Tax...it was just a test to see if it works..and it did.

Basically i'm looking for some help from someone that's good with tax etc...Because i'm totally lost!

Will upload my project if you anyone wants to see it all...Its dreadful mind!

Thanks.