Under-construction vs ready-to-move, a decision framework with numbers

Every Indian home buyer eventually faces this fork: a ready flat you can walk into next month, or an under-construction one that costs less today and promises more tomorrow. The right answer depends on four numbers, not on temperament. This framework puts them on one page, with the RERA-era tools that changed the risk side of the equation.

Number 1: the price gap#

Builders price time and risk into launches. In comparable locations, under-construction inventory at launch typically sells 10 to 25 percent below ready flats, narrowing as the project approaches completion. On a Rs 1 crore ready flat, the equivalent under-construction unit might book at Rs 80 to 90 lakh two to three years before possession.

That discount is not generosity. It is the market paying you to accept construction risk, waiting cost and uncertainty. The whole decision is whether the payment is adequate for the risk of the specific project in front of you, which is exactly what the other three numbers measure.

Number 2: the tax asymmetry#

GST applies at 5 percent on under-construction homes (1 percent for affordable housing), with no input tax credit, on top of stamp duty and registration that both options pay. Ready-to-move flats with a completion certificate attract no GST at all.

On a Rs 90 lakh under-construction agreement value, GST adds Rs 4.5 lakh. So the honest price comparison is: under-construction price plus GST plus waiting cost, against ready price. A 20 percent sticker discount shrinks to roughly 15 percent after GST. Still meaningful, no longer dramatic. Where every one of these charges lands on the calendar is mapped in the money timeline of buying a flat.

Number 3: the rent-plus-EMI overlap#

If you live on rent while your under-construction flat is built, you pay rent and EMI simultaneously once the loan disburses. Suppose Rs 30,000 monthly rent and a Rs 55,000 EMI on the disbursed amount, for a 30-month construction period: the overlap costs around Rs 9 lakh before your first night in the flat, more if handover slips. Buyers routinely ignore this line item, and it is frequently larger than the GST.

There is also an income tax wrinkle: interest paid during construction is only deductible in five instalments after possession, within the usual limits for self-occupied property, so the overlap period gives you the cost without the timely deduction.

Number 4: the delay probability, now measurable#

Before 2017, delay risk was folklore. Today it is a public record. Every registered project files a completion date, extension history, quarterly construction percentages and quarterly sales figures. Every promoter's past projects show promised versus delivered dates. Nationally, regulators had disposed of over 1.47 lakh complaints by September 2025, the largest share about delays, so the base rate is not trivial (your remedies, if it happens, are in the delayed possession guide). But base rates are not your rate: your rate is the specific promoter's record, and that is readable in advance.

A practical scoring shortcut for the project you are considering:

• Promoter delivered its last two projects on or near time: strong positive.
• Current project's construction percentage rising steadily each quarter: positive.
• Bookings above the area median at the same stage: positive, since sales fund escrow-backed construction.
• Any extension already taken, or filings gone quiet: strong negative.

Our guide on checking a builder's track record turns this into a repeatable method, and each ReraGenie project page shows the quarterly trendline next to the area's numbers.

The decision table#

Choose ready-to-move when: you need the home within a year; rent-plus-EMI overlap would strain you; the GST saving matters at your budget; you value certainty over upside; or the specific under-construction alternatives have weak filings. Ready inventory itself splits into the developer's unsold stock and owner resales, a fork with its own trade-offs covered in resale flat vs new booking.

Choose under-construction when: your timeline is flexible; the effective discount after GST and overlap still clears 10 to 15 percent; you want new-launch choice of floor and stack; and, non-negotiably, the promoter's record and the project's quarterly numbers pass inspection.

The hybrid worth knowing: nearly-ready projects, past 80 percent construction with an OC application in sight, often combine most of the discount with a fraction of the risk, and GST still applies only if you buy before the completion certificate. Watch for these in filings: construction percentage high and climbing, OC expected within two or three quarters.

A note on payment plans#

Under-construction purchases come wrapped in payment plans, and the plan changes the risk more than most buyers realise (the full plan-by-plan comparison measures each one by the money trapped if the project stalls). Construction-linked plans, where instalments follow certified construction stages, keep your money roughly in step with the asset and are the RERA-friendly default. Time-linked plans collect on calendar dates regardless of progress, shifting risk to you: avoid them unless the discount is exceptional. Subvention-style offers, where the builder pays your interest until possession, have been restricted by regulators and lenders over the years precisely because buyers ended up liable when builders defaulted. Whatever the plan, two rules hold: not more than 10 percent before the registered agreement, and instalments that reference certified construction stages you can verify in the quarterly filings.

The one-line summary#

Ready-to-move is buying certainty at full price. Under-construction is selling certainty for a discount. RERA's public filings let you measure, project by project, whether the discount on offer actually pays for the risk you are taking, which is a calculation, not a gamble, for anyone willing to read.