Stamp duty and registration on an agreement to sell are not uniform across India, and the difference can run into lakhs of rupees, so the State where the property sits matters more than any other single factor.
Maharashtra treats the agreement to sell with unusual seriousness. Under the State stamp law an agreement for sale of immovable property is stamped close to conveyance rates, and registration is effectively mandatory for flats, which is why Mumbai and Pune buyers routinely register the agreement itself rather than waiting for the deed. The Maharashtra Ownership Flats Act and RERA together push registration of the agreement for sale to the front of the transaction.
Karnataka follows the RERA pattern closely for under-construction property, with the State authority notifying the agreement-for-sale format that promoters in Bengaluru must use. Stamp duty on the agreement is lower than on the final sale deed, but the deed still attracts the full rate at completion, so buyers should budget for both stages rather than assuming one payment covers everything.
Delhi and the National Capital Region see heavy use of the older SA/GPA/Will route to avoid stamp duty, a practice the Supreme Court discouraged in Suraj Lamp. Relying on a power of attorney instead of a registered sale deed leaves a Delhi buyer without legal title, however convenient it looks at signing. A properly stamped agreement to sell followed by a registered deed is the only safe path.
Tamil Nadu and several southern States apply their own stamp schedules and require the agreement to be presented for registration within four months of execution under the Registration Act 1908, with penalties for delay that the sub-registrar may, in limited cases, condone. Buyers of agricultural land in States such as Karnataka, Telangana and Himachal Pradesh face additional restrictions on who may purchase, so the agreement should be conditional on the required revenue-department clearance.