It saves some money, but still very little compared to the tax bill for the average nanny.
What is the average tax bill?
Lets say the nanny is paid £8 per hour gross.
Works 50 hours per week, thus £400 gross per week. 52 weeks = £20,800 gross per year. £15,856.54 net pay 2006/07 tax year - net pay figure from Listen To Taxman - UK PAYE calculator or put another way 304.93 per week, or a little over £6 per hour net.
According to the UK PAY calculator , Employers NI is £38.78 per week based on £400 gross salary. So times 52 = £2016.56 per year.
Childcare vouchers for one parent, is worth £243 per month, thus £2916 per year.
Not fully sure how much of that childcare voucher parents are not taxed on, possibly all of it, thus in this example, the annual voucher amount is more than the annual Employers NI bill.
So yes it does cost more usually to have a nanny, but at least using an Approved Nanny and part-paying with Childcare Vouchers does help a bit towards the tax (or to be more precise the NI) bill.