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Use the SA401 to register as a partner for Self Assessment and Class 2 National Insurance contributions.
To register you can:
use the online service (you’ll need to log in to your tax account)
fill in form on-screen, print and post to HM Revenue and Customs
You should fill in the form fully before you print it as you can’t save a partly completed form so you should gather all your information together before you start to fill it in.
If you’ve problems opening the online forms you can use the PDF version, you’ll have to print this and fill it in by hand before posting it to HMRC.
Before you start
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