In Tamil Nadu the certificate that matters is the completion certificate (CC), issued by the authority that granted the planning permit: CMDA, DTCP or the local body. If the building legally needed a CC and does not have one, buying a flat in it is not safe: the rules say permanent power, water and sewer connections should follow the CC, and the Madras High Court has directed that possession be handed over only after it. The exception is small residential buildings, which the rules exempt from a CC altogether.

Updated 13 October 2026. We read TNCDBR 2019 rule 20 and its 2024 amendment, TNRERA's proceedings of 16 June 2026 on project completion, CMDA's published CC lists and two Madras High Court rulings, plus the leading competitor explainers, which treat OC and CC generically and miss the Tamil Nadu exemptions.

What is OC in an apartment, and what is a CC in Chennai?

Nationally, an occupancy certificate (OC) says a building is fit to occupy and a completion certificate says it was built as per the approved plan. Tamil Nadu's building rules are organised around the completion certificate, certifying that the building has been completed as per the approved plan, and the CC is what triggers service connections. The rules do mention an “occupancy certificate as applicable”, so ask for whichever the approving authority issued, but in Chennai the CC is the document you will almost always be shown.

For a national comparison of the two documents, see OC & CC: Why You Should Never Buy a Home Without Them.

Which buildings need a completion certificate in Chennai?

TNCDBR rule 20(1) requires a CC for all buildings except small residential buildings and industrial buildings. The original exemption covered residential buildings up to 12 m in height with not more than 3 dwelling units or 750 sq m. G.O. Ms. No. 70 of 11 March 2024 raised the unit count to 8, keeping 750 sq m; press reports at the time, including Outlook's, said companion amendments raised the related height limit to 14 m.

  • Needs a CC: apartment complexes with more than 8 units or above 750 sq m, high-rises, commercial and mixed-use buildings.
  • Exempt: an independent house, or a small residential building within the 8-unit and 750 sq m limits and the height cap.
  • Self-certified homes (see Self Certification Building Approval in Tamil Nadu: 2026 Rules) sit inside the exemption by size.

Can I buy a flat without OC or CC?

It depends entirely on which group the building falls into.

  • New flat in a project that needed a CC: do not take possession or pay the final instalment without it. The builder's own obligations under TNCDBR include not handing possession to anyone before the CC or OC.
  • Flat in a small building within the exemption: a missing CC is not by itself a defect. Instead check the planning permit and approved plan, and confirm the floors and units built match them.
  • Resale flat: ask for the CC if the building needed one, plus the approved plan. A building that added floors or units beyond its permit may have tipped over the exemption limits.
  • Independent house: ask for the building permit and approved plan; a CC is usually not required, but unauthorised additions are still a risk.

What does TNRERA now require before a project counts as complete?

TNRERA's Proceedings No. TNRERA/A3/1840/2026-2, dated 16 June 2026, set out the forms a promoter must file to intimate completion of a registered project. For a building project, Form I asks for:

  • The completion certificate reference from the competent authority, or an architect's or engineer's CC where a CC from the planning authority is not mandatory.
  • An architect's certificate in Form 4, including the structural engineer's certificate of soundness.
  • A declaration, with proof, of water supply, sewerage (CMWSSB or local body connection, a functioning STP, or septic arrangements) and electricity connections, plus a lift inspector's certificate that the lifts work.
  • A declaration that all amenities promised in the approval, agreement and brochure have been provided and are functional.
  • Geo-tagged photographs: four of each block, two of each common amenity, and four aerial photos of the whole project.
  • Audited statements of the three RERA bank accounts, details of complaints pending, and a ₹5,000 scrutiny fee.

How do I verify a completion certificate in Chennai?

Ask the seller or builder for a copy, then check it against the authority's own record rather than trusting the paper alone.

  • CMDA buildings: CMDA publishes year-wise Completion Certificate Issued Lists on cmdachennai.gov.in, showing the planning permit number and date, the site address with survey number, what was completed (for example, stilt plus four floors with 8 units), and the CC number and date.
  • Match every field: survey number, village, permit number, number of floors and dwelling units. A CC for “stilt + 4” does not cover a fifth floor.
  • Partial CCs exist for phased projects, so confirm your block or tower is the one named.
  • Buildings approved by the Greater Chennai Corporation, DTCP or a panchayat: ask that office, or search the Single Window Portal's approved plan list (see CMDA Approval Check Online: Verify a Flat or Plot in 2026).
  • A letter from a panchayat president is not a completion certificate: the Madras High Court held so in January 2025, noting that in the Chennai Metropolitan Area the competent authority is CMDA.

What if the builder says the CC has been applied for?

Ask for the acknowledgement of the CC application and its date. TNCDBR rule 20 gives the competent authority 30 days from receipt of a completion application to communicate its decision after inspection, and makes it obligatory for the applicant to confirm the lift inspector's and fire service certificates where they apply.

A CC pending for months is a reason to ask why. When the Madras High Court ruled on completion certificates in 2022, it said officials must inspect the site and any deviation from the approved plan must be rectified before a certificate is issued. Until the CC arrives, keep your final payment and your possession acceptance tied to it in writing.

What happens to home loans, EB and water connections without a CC?

TNCDBR rule 20 says service connections such as electricity, water supply and sewerage are to be given only after the CC is produced, and that temporary construction connections must not continue after completion. In practice, a flat without a required CC can leave you on construction power or tanker water.

Lending is affected too. In August 2022 the Madras High Court directed CMDA and the Greater Chennai Corporation to take undertakings that buildings will be handed over only after a CC, and said banks should get the CC before sanctioning loans for such properties. And a missing CC follows the flat into resale, when the next buyer's lawyer and bank will ask for it.

Does the August 2026 reform mean small homes no longer need a CC?

Not quite. The August 2026 announcement raised the self-certification limit to 5,000 sq ft and introduced third-party certification up to 8,070 sq ft, but it did not change rule 20. Small homes were already exempt from a CC because of their size, and a 5,000 sq ft G+2 home would also be below 750 sq m. The detailed order for the new limits was not yet available on 13 October 2026.

Exemption from a CC is not exemption from the approved plan. Authorities can inspect self-certified buildings at any stage and require violations to be removed.

New flat or resale independent house: what to ask for

Two short checklists.

Is it safe to buy without OC or CC? Our verdict

For a flat in a building that needed a CC, wait for it or walk away; the money and time you save rarely cover the risk to utilities, loans and resale. For a small building or independent house within the exemption, a missing CC is normal, so shift your diligence to the approved plan and what was actually built.