Employer did not deduct tax - underpayment

[essayer]

OH has just received a tax bill seemingly related to 2010-2011 when she changed her job and her new employer did not deduct any tax for one month.

HMRC have now worked it out and sent a P800, presumably they deduct it through the tax code.

I know there was some question at the time about her previous employer not giving her a P45 immediately, but how have they ended up not paying any tax at all? Aren't they supposed to use the normal tax code until notifed otherwise?

Does this make them responsible for the error and also the underpayment? HMRC seem to make provision for this ..

[Eric Mc]

You need to find out why the tax was incorrectly calculated.

Ultimately, a taxpayer is always respnisble for ensuring they pay the correct tax - even under the PAYE system.