My employer has agreed to maternity pay of 8 weeks full pay, 18 weeks at 50% pay and final 13 weeks at SMP rate. I will be on maternity leave for one year in total and this will start in a new financial year. Could you advise how they should be taxing this/ or how I can work out how much tax I should be paying on this?
All Maternity Pay is taxable. (However Maternity Allowance as a benefit is not.)
You may have heard stories of other mums getting big tax refunds when they went on maternity leave but to qualify for the refund you have to actually have paid the tax in the tax year. This is unlikely in this case.
The good news, though, is that in the 2013-2014 tax year the standard Personal Tax Free Allowance rises to £9,205. If your total earnings in the tax year are less than this figure then you will not pay any tax.
I am assuming that you have no other taxable income or benefits which would reduce your tax free allowance.