This is not a problem, verification is possible even with an expired ID card. During the check-out process, our system will show you that the verification was not successful, but we can still see your ID card in our system.
Please note: In this case, we also require proof of your address in the form of a registration certificate no older than 12 months. You can send this directly by e-mail to support+dokumente@finn.com. If you do not have a (current) registration certificate, you can easily apply for one at your citizens' registration office.
We have summarized all alternative identity documents that you can use for verification in this article.