Under the P38S procedures, students who work during the Christmas holidays may be able to be paid tax-free if their earnings for the tax year will not exceed their personal allowance (£6,475 for 2010/11).
The P38S procedures apply only to students who work during the holidays only and not to term-time working. Further details of the procedures are available on the HMRC website.
HMRC also produce a student tax calculator, which is available on the HMRC website.
The P38S procedures are due to be replaced by a student tax code.