Hi,
I see no real error in your syntax, although I would not write it like this. What data type does the field Angebotsnummer have?
Have you checked the value of the criteria, using a break point or with
Debug.Print Forms![Checkliste Angebot]![Angebotsnummer]
and then have a look at the result in the Immediate Window?
You could also try to formulate the filter differently. Maybe you'll get an error message because of data types or the like. Based on your object names, I assume you understand German. Then take a look at this syntax variant.