Your tax code is your personal allowance...ie, What amount you can earn before tax, for example a Tax Code could be JL5460, Meaning your personal allowance is £5460....Its tax free up that point, then a anything over £5460 is taxable...But there are deductions, allowances and add backs that will all deduct from this as well.
If your working in building for examples, as a sub contractor and getting tax deducted each week, it will be at a higher rate of usually 40%...But when your accountant tallys up your personal allowance, then expenses such as work wear, tools, telephone, use of office e