What it is
tnreginet.gov.in is the online portal of the Tamil Nadu registration department, distinct from the revenue department's eservices.tn.gov.in. It is where you apply for an encumbrance certificate for a survey number and period, check the guideline value the registration department has set for a locality, and access other registration-related services such as document search for registered deeds. It is organised by the same district, taluk and SRO jurisdiction structure used elsewhere in the land-records system.
Why it matters when you buy
Two of the most important pre-purchase checks run through this portal: pulling the encumbrance certificate to see the property's recorded transaction history, and checking the guideline value, which sets the floor for the stamp duty and registration fee you will pay on the sale deed. Because the registration department, not the revenue department, issues the encumbrance certificate, this is the site to use for that, not eservices.tn.gov.in.