Your daughter should have registered with HMRC as Self Employed and already started paying Class 2 National Insurance contributions, which are payable monthly by Direct Debit. Contributions for the 2011/12 tax year start being collected this month for the month of April as they are now being collected 4 months in arrears.
Dependent on her profit, she will also be liable to pay Class 4 contributions, which are worked out at the same time as her Self Assessment tax return.
It is advisable to save the approximate amount of tax payable, as this is charged in arrears, in two tranches, although her first payment will be for the tax year ending 5th. April 2011 and is payable by 31st. January 2012, together with a first payment on account for the tax year 2011/2012 of half of the estimated tax that would be payable. The second payment on account is then due to be paid by 31st. July 2012.
See the following link:
http://www.hmrc.gov.u...ntro/selfemployed.htm