HMRC have amended the form CWF1 which is completed by those individuals who have set up a new business either as a sole trader or as a partner in a partnership. The form is used to notify liability to Class 2 National Insurance Contributions (currently £2.40 a week) amongst other things.
Under the revised behaviour based penalties, which apply from April 2009 anyone becoming or ceasing to be liable to pay Class 2 NICs must notify HMRC as soon as possible. Penalties may be charged where the liability is not notified by 31 January following the end of the tax year when they became liable.
You can find the form (PDF) here: Form CWF1