I am an Orthodox Jew. I married my second wife in a Reform ceremony as she could never prove that she was Jewish (but was able to satisfy the Reform rabbi at the time that she was Jewish, on her mere say so). She has absolutely no documentary evidence of being Jewish in the form of any synagogue or burial records, despite her claim to me that she was completely Jewish on her mother's side. I accepted this and we have lived a fairly observant Jewish life for the past 8 years. However, all existing records show that her maternal great-grandmother was baptised in Church as far back as 1888 and there has never been a single Jewish marriage or connection since then.

We have now separated and plan to divorce.

Question: do I need a Get? I believe the answer is no, I would however appreciate some guidance if possible.

Thank you for reaching out to us.  I appreciate the commitment shown in asking for halakhic guidance at such a difficult personal time.

I think it is in your best interest to arrange for a get. You may well be correct that your wife is not halakhically Jewish, but should you at some point be interested in remarrying, the burden of proof will be on you to demonstrate that, and it's hard to prove a negative. If your wife refuses to cooperate, a beit din would likely be willing to investigate and formally declare you halakhically free, but the get is safest.

Please tell me if this is helpful, and I'm happy to answer any followup or further questions.

Wishing you only happiness in the future