Canadian Citizen with OCI living in India permanently.

No intention of ever coming back to Canada, gone back to India for good, but will maintain Canadian citizenship and CAD passport, and will live in India permanently as an OCI.

Won't take Indian citizenship, will remain a Canadian citizen living in India on OCI for good.

Only bank accounts in India are currently NRO and NRE accounts.

Do these NRO/NRE accounts have to be converted back to Resident Indian accounts? Or can they be kept as NRO/NRE accounts, due to Canadian citizenship & OCI card?

Since now you're a resident of India for tax purposes, even though you're a Foreign citizen, I am guessing NRO/NRE accounts can't be maintained.

Tax returns will be filled in both countries.

Bump