thanks everyone
yes she changed jobs in April and was put on emergency tax but last month and this month her tax code has been 543L.
no there is no other deductions,she does not pay into the pension scheme/BUPA until she has been there 6 months.
yes she is paid monthly not four weekly
her pay office are checking it but have told her that if there is a mistake she will have to claim a refund from the tax office.Surely the pay office should put it right?