Stamp Duty on Under-Construction vs Ready Flats 2026

You've booked an under-construction flat, paid a booking amount, and now the builder's team wants you to sign an "agreement to sell." Somewhere in that document is a stamp duty figure — and you're not entirely sure why you're paying it now, months or years before the flat is even ready. Is this the full duty? Will you pay again at possession? And why does the builder also want GST on top?

These questions trip up nearly every first-time buyer choosing between a builder's under-construction (UC) project and a ready-to-move (RTM) resale flat. The timing and structure of costs are genuinely different between the two, and misunderstanding them can throw off a cash-flow-sensitive buyer's budget by a significant margin. This guide walks through exactly when stamp duty is payable on a UC flat, how GST layers on top, and how the total cost picture compares to buying ready.

The Agreement to Sell Is the Chargeable Instrument

For a builder-sold under-construction flat, the key document is the agreement to sell (also called the "agreement for sale," and increasingly standardized in form under RERA). In most states, this agreement — not a later conveyance deed at possession — is the instrument on which stamp duty becomes chargeable, because it is the document that creates enforceable rights over the specific unit and records the sale consideration.

This means: stamp duty on a UC flat is typically paid at the time the agreement to sell is registered, not deferred to possession. The exact percentage and the base value it's calculated on (agreement value vs the state's ready reckoner/guidance/circle value, whichever is higher) follow the same state stamp act framework used for any other property purchase. There is no special "under-construction rate" that is separate from a state's standard stamp duty schedule — what differs is only the timing in the transaction lifecycle at which the duty becomes payable, and the fact that a second document (a deed of conveyance, formally transferring the completed structure) may sometimes be required at a later stage in a few states' frameworks.

According to IBEF's Real Estate Industry in India report (February 2026), the sector logged FY25 project delivery of over 4 lakh units (up ~33% year-on-year), with new launches continuing to dominate several major markets — underscoring how common the under-construction purchase path remains for first-time buyers, and why understanding its cost sequencing matters.

Step-by-Step: The Under-Construction Purchase Timeline

A typical UC flat purchase moves through these stages, each with its own cost trigger:

1. Booking amount. A token payment (often 1–10% of the total price) to hold the unit. No stamp duty is due at this stage — this is a pre-contractual payment, not a registered instrument.
2. Allotment letter. The builder confirms the unit, floor, and price. Still generally not the stamp-duty trigger point on its own.
3. Agreement to sell (registration). This is where stamp duty (and registration fee) becomes payable, calculated on the higher of the agreement value or the applicable ready reckoner/guidance/circle value for that locality. This is also typically when GST first becomes payable on the portion of consideration linked to that stage, since GST is charged progressively as construction-linked payments (CLP) are invoked.
4. Construction-linked payment milestones. As the builder completes slabs, structure, finishing, etc., you pay per the CLP schedule, and GST applies to each installment (for UC properties) at the applicable rate as notified under GST law from time to time.
5. Possession and occupancy certificate (OC). Once the project receives its OC, the unit is treated as "completed," and no further GST applies on any remaining payment made after OC issuance. Some states also require execution of a conveyance/sale deed at or after possession to formally transfer title, which itself may carry a nominal or full duty depending on how the state treats the earlier agreement-stage payment (adjustment/credit rules vary by state — verify locally).
6. Registration of the flat/society records, mutation. Post-possession administrative steps, generally involving nominal fees rather than fresh stamp duty in most states, once the earlier agreement/deed has been duly stamped.

Under-Construction vs Ready-to-Move: Cost & Timing Comparison

Always confirm the GST rate in force at the time of your purchase directly with the builder's finance team or a tax professional — GST rates and conditions on real estate have been revised by the GST Council over time, and using a stale rate in your own budget can create a meaningful shortfall.

Maharashtra and Karnataka: How the Rule Plays Out Locally

• Maharashtra (Mumbai, Pune, and other cities): Stamp duty on the agreement to sell for a UC flat is calculated on the higher of the agreement value or the "ready reckoner" rate notified annually for that specific area and building type. The agreement must be registered, typically within the period prescribed under the Registration Act, and the duty is paid before or at registration.
• Karnataka (Bengaluru): The equivalent reference value is the "guidance value" published by the Department of Stamps and Registration, revised periodically. As in Maharashtra, duty is charged on whichever of agreement value or guidance value is higher, at the point of registering the agreement to sell.

In both states (and most others), if your agreement value looks artificially low relative to the published guidance/ready-reckoner rate for that area, expect the duty to be computed on the higher official rate — this is a common surprise for first-time buyers who assumed their negotiated price would be the sole basis for duty.

Real-World Scenario: Sequencing Duty and GST Across a CLP Schedule

Consider a first-time buyer in Pune booking a 2BHK apartment in a project still under construction, priced at a total consideration with a standard construction-linked payment plan. At booking, the buyer pays a token amount — no duty, no GST yet. Within a few weeks, the buyer signs and registers the agreement to sell; at this point, stamp duty (calculated on the higher of agreement value or the area's ready reckoner rate) becomes payable in full, along with the registration fee, and GST becomes due on the installment tied to that stage.

Over the following 18 months, as the builder completes the structure, flooring, and finishing, the buyer makes each CLP installment, and GST applies to each one at the applicable rate in force at that time. When the project receives its occupancy certificate and the buyer takes possession, no further GST applies to the final payment made after OC issuance. Because the agreement to sell was already registered and stamped upfront, the buyer does not pay stamp duty a second time at possession under Maharashtra's framework — though buyers in other states should independently confirm whether their state requires an additional deed of conveyance step with its own duty treatment.

The lesson: the biggest one-time cash outflow (duty + registration) typically lands early, at agreement registration — not spread out and not deferred to the end — which is exactly why a buyer's early-stage budget needs to account for it upfront rather than assume it's a possession-time cost.

RERA Registration and the Agreement's Role

Under the Real Estate (Regulation and Development) Act framework adopted by each state, most under-construction projects above the notified size threshold must be registered with the state RERA authority before the builder can market or sell units. The agreement to sell used in a RERA-registered project generally follows a standardized format prescribed under the state's RERA rules, covering disclosures like the carpet area, project timeline, and payment schedule.

RERA registration of the project does not change stamp duty rates or timing — duty is still governed entirely by the state stamp act — but it does mean the agreement you're registering (and paying duty on) should reflect RERA-mandated disclosures, giving you a documented basis to hold the builder accountable to the payment and delivery schedule.

Pro Tips

• Ask for the total-cost breakup upfront — booking amount, duty + registration at agreement stage, GST per CLP milestone, and any possession-stage charges — before committing, so there are no cash-flow surprises mid-construction.
• Check the current guidance/ready-reckoner value for the specific locality before signing, since duty is calculated on the higher of that value or your agreement price.
• Confirm the current GST rate and applicability directly with the builder or a tax professional at the time of each payment — rates and rules have changed over the years.
• Keep every registered agreement and payment receipt — these documents matter later for loan disbursement, resale, and any future dispute over the payment schedule.
• Don't assume duty is deferred to possession — for most states, it's due at agreement registration, and budgeting as if it's a possession-time cost can leave you short early in the process.

Common Mistakes to Avoid

• Assuming GST applies at possession — it typically applies progressively through construction-linked payments, and stops once the OC is issued.
• Under-declaring the agreement value expecting to reduce duty — the state will compute duty on the higher of agreement value or guidance/ready reckoner value regardless.
• Confusing RERA project registration with stamp duty compliance — they are separate legal requirements under different laws.
• Not budgeting for registration fee separately from stamp duty — most states charge these as two distinct line items.
• Skipping verification of the project's RERA registration number before signing the agreement, which can affect your legal recourse later.

How DrawMagic Fits In

Sequencing stamp duty, GST, and construction-linked payments correctly is exactly the kind of planning problem DrawMagic's free tools are built for:

• Use the Stamp Duty Calculator to estimate duty and registration charges on your agreement value before you sign, so there's no surprise at the registrar's office.
• Once you take possession, the Property Tax Calculator helps you estimate your ongoing annual municipal outgo on the new unit.
• Map the entire booking-to-possession cash flow — duty, GST milestones, and CLP installments — with DrawMagic's financial planning tools for buyers, so your monthly budget survives the full construction period.
• Explore DrawMagic's broader resources for buyers for more on comparing under-construction and resale options.

These calculators are free; if you want more structured, ongoing support through a multi-year construction-linked purchase, see DrawMagic's plans.

Key Takeaways

• Stamp duty on an under-construction flat is generally charged when the agreement to sell is registered — not deferred to possession — and is calculated on the higher of agreement value or the state's ready reckoner/guidance value.
• GST applies progressively on construction-linked payments for under-construction units but does not apply to a completed, occupancy-certified unit — a real cost difference versus a ready-to-move purchase.
• Some states may require an additional deed step at or after possession; confirm your state's treatment and any duty-adjustment rules before assuming a single registration event covers everything.
• RERA project registration is a separate legal requirement from stamp duty and does not change duty rates or timing.
• Always verify the current GST rate and any applicable conditions with the builder's finance team or a tax professional before finalizing your budget.
• Duty is computed on the higher of your agreed price or the government-notified guidance/ready reckoner value — under-declaring the agreement value will not reduce your duty liability.
• The largest one-time cash outflow typically lands early, at agreement registration, so budget for it upfront rather than assuming it's a possession-stage cost.
• Use the Stamp Duty Calculator before signing to avoid a mismatch between your budget and the registrar's computed duty.

FAQ

Q: Do I pay stamp duty twice — once at agreement and again at possession? A: In most states, no — duty paid at agreement registration covers the transaction, though a few states have a separate conveyance-deed step at possession with its own treatment. Confirm your state's specific rule before assuming either way.

Q: Is GST charged on the full flat price or just the construction-linked installments? A: GST is generally charged on each construction-linked payment as it falls due, at the rate in force at that time, and stops once the occupancy certificate is issued and the unit is treated as complete.

Q: Does a lower agreement value reduce my stamp duty on a UC flat? A: No — the state computes duty on whichever is higher between your agreement value and the official guidance/ready reckoner value for that locality, so under-declaring the price does not reduce your duty liability.

Q: Can DrawMagic tell me the exact current GST rate for my project? A: No — DrawMagic is an information and calculation platform, not a tax advisor. Confirm the current GST rate and applicability directly with the builder's finance team or a licensed tax professional.