If you are a UK employer or agent, and you’re sending an employee to work in another country within the European Economic Area (EEA), check which member state's social security legislation applies. 

You also need to inform the HMRC, as this will allow them to work out which legislation applies and allow you to find out if your employee needs to continue paying UK National Insurance contributions while they temporarily work abroad.


If it is the first time your company has contacts with the UK authorities about sending employees to another country you should fill in form CA3821. This can be done online or (particularly if your organisation has been trading in the UK for less than 18 months) via post.

NOTE: to apply online through gov.uk, you will need a Government Gateway ID and password. If you don't have them, you can create one when you start your application.


If the employee will be simultaneously working in 2 or more EEA countries, use form CA8421 instead.


You will need to check with the employee: 

  • if they have changed their name, if so you need their previous name
  • if they have changed nationality, if so, what nationality were they before and the date it changed 


If they have gained a British citizenship since moving to the UK before filling in this form, they need to write to HMRC and give the date they gained citizenship and to send in their original passport or a certified copy quoting their National Insurance number.

 A certifying office or organisation must stamp the copy and their representative must sign it.

A certifying office could be:

  • government department
  • legal organisation
  • medical body
  • mayor’s office
  • British Consulate


Check with the employee if they have been self employed in the last 5 years, if so are they keeping their business whilst working overseas.

If they were self employed and have stopped and they did not tell HMRC, they need to contact HMRC as this may delay their application.


If your employee worked abroad in the last 5 years, they need to provide the:

  • name of their employers
  • dates they worked
  • countries they worked


If you or the employee has previously had an A1/E101 which overlaps with the period you’re applying for, HMRC may not be able to process your application.

If you are applying for an extension to a previous A1/E101, enter the date as the day after your existing one expired, or is due to expire.


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