[nsteel]

And in the case where you don't/can't provide a P45 they take an "emergency" high rate of tax instead. Which you can claim back once the information is provided, or at the end of the tax year. I don't know if you can legitimately decide to not provide a P45 for some personal reason, but it could be an expensive decision (in the medium term).

I would say this definitely reflects your personal stance on privacy, I think most people would rather have the money they earned sooner rather than later.