The English term applies to a Zeugnis as an employee reference letter, often referred to in its entirety as "Arbeitszeugnis".
There are multiple definitions - click on the translation that matches your context.
(also: letter of reference/reference letter) a letter containing information about you and written by someone who knows you well, especially one to be sent to a potential employer, university or landlord etc
A good character reference letter helped her get employment.
a mention of something in a speech, a piece of writing or an artistic work etc
We should normally avoid references to commercial products.
a letter in which an employer, former employer, teacher, professor, or other authority figure recommends an employee to a potential future employer for a new job
She asked her college tutor for a reference with regard to employment.