Extending a posting period
If your employee needs to work outside the Netherlands for longer than the end date stated on the A1 certificate (certificate of coverage), you can extend the A1 certificate online via TWinternet.
If you do not have an account yet, apply for this first. Otherwise, the only way you can inform us of a change is by making a new application in writing.
If the original application (for the A1 certificate that you want to extend) was sent to us in writing, you should inform us of the change by sending us a new application in writing.
Even if you have informed us of a change online, we may sometimes have to ask you to make a new application as well. For example, if the change means that the total posting period would be longer than the period allowed by law. In that case, we have to submit the application to the social security organisation in the other country.