Alternates to marriage certificate

[sunnyday7]

Hi, I married my wife who also had a green card at the time of marriage. Due to timelines, we couldn't register our marriage in India. We soon returned to USA. So we don't have a marriage certificate.

I am currently 7 years into since my green card and eligible to apply for naturalization. I would need a a proof of marriage for the final interview and also just in case if it is needed prior to that.

 Since we don't have a marriage certificate, I am wondering if there are alternate proofs that USCIS would accept.

• If anyone who had been married has submitted n400 without marriage certificate, please share your experience? What alternate proofs are acceptable?

I have saved my son's school registration certificate, tax transcripts and our family health insurance records to prove that we are husband/wife.

Thanks in advance.