After nanny is issued with her P60, she may look at it and query some of the details.
One common question from both nanny and the employer is that the total gross pay is too low. The gross pay is for the previous tax year only, not the whole of the employment and may also include earnings from a previous employer if nanny started part way through that tax year.
Another query regarding the pay is that it is too high. If nanny is paid a net salary say £1000 a month, they would expect the pay to say £12,000. However, that is the net salary, the tax, employee national insurance, employee pension costs and student loans are on top of this and then added to the net to give the gross salary.