GST registration: the process, and the 30-day trap

Short answer: you have 30 days from becoming liable to apply. With Aadhaar authentication the application is normally deemed approved in seven working days; without it, expect physical verification and around twenty-one.

The part almost nobody is told: applying within those 30 days is what preserves input tax credit on the stock you are holding when you register. Miss the window and the registration still happens — the credit does not.

When the clock actually starts

The obligation arises when you cross the threshold or fall into a compulsory category under Section 24, not when you get round to dealing with it. From that date you have 30 days to apply.

Whether you are liable at all — the ₹40 lakh and ₹20 lakh thresholds, and the Section 24 cases that override them entirely — is set out on the GST registration and return filing page. A trader selling through a marketplace, or a consultant with one client in another state, is frequently liable well below the threshold.

The process

1. Form REG-01, Part A. PAN, mobile number and email. These are validated and you receive a Temporary Reference Number.

2. Part B. The substance: constitution of business, principal and additional places of business, bank details, goods and services with HSN or SAC codes, and details of promoters or partners.

3. Aadhaar authentication. Under Section 25(6A) to (6D), you elect whether to authenticate via Aadhaar. This choice drives everything that follows.

4. Biometric verification, now in every case. Until September 2026 this step applied only where the portal's risk analysis flagged the application under Rule 8(4A). On 8 September 2026 the Delhi High Court, in Neha v Union of India (W.P.(C) 12210/2026), directed all authorities across the country not to grant any GST registration without biometric-based Aadhaar authentication. The petitioner had found two registrations obtained on her stolen PAN and Aadhaar and used to attempt a ₹4.46 crore fraud on her bank account; the court noted 2,800 such registrations detected in 2023-24 and 1,654 in 2024-25. The direction is interim and the matter is listed again on 22 September 2026, but until it is varied, every applicant, or each promoter, partner and authorised signatory where the portal requires it, attends a GST Suvidha Kendra in person for biometric authentication and document verification, and the application does not generate an ARN until that is done. Plan the visit into the timeline rather than treating it as a contingency.

5. Approval, or a query.

One operational trap worth knowing: the verification steps have to be completed within 15 days of submitting Part B, failing which the application does not proceed to an ARN. An application started and left half-finished does not sit patiently waiting.

The 30-day trap — where the money is

This is the part that turns a scheduling question into a financial one.

Section 18(1)(a) entitles a newly registered person to input tax credit on inputs held in stock, and inputs contained in semi-finished and finished goods, as on the day immediately preceding the date from which liability arose.

But it is conditional:

• It is available only where the application was made within 30 days of becoming liable.
• It must be declared in Form ITC-01, filed within 30 days of registration being granted.
• The declaration can be made only once.
• Invoices can be up to one year old for inputs, and up to five years for capital goods in the situations where those qualify.

So a business that crosses the threshold in April, carries on trading, and gets round to registering in August faces three separate losses: the stock credit is gone, the tax on supplies made in the meantime is still payable, and interest runs on it.

The delay is usually thought of as a paperwork lapse with a late fee attached. On a business holding meaningful stock, the forfeited credit is frequently the largest number in the whole exercise — and it is unrecoverable, because ITC-01 can only be filed once and only within its window.

What you will need

• PAN of the business and of promoters or partners
• Aadhaar of the authorised signatory and promoters
• Constitution proof — partnership deed, certificate of incorporation, or equivalent
• Proof of principal place of business — ownership document, or rent agreement together with the owner's ownership proof and a no-objection letter
• Bank account proof — cancelled cheque, statement or passbook page
• Photographs of promoters and the authorised signatory
• Authorisation letter or board resolution for the authorised signatory
• Digital signature, where the entity is a company or LLP

The place-of-business documentation is where applications most often stall. A rent agreement without the landlord's ownership proof, an address that does not match the electricity bill, or a shared or virtual office without adequate supporting documents are the recurring causes of a REG-03 query.

Voluntary registration — when it is worth it

Section 25(3) allows registration below the threshold. It is worth considering where:

• your customers are registered businesses who need the credit on what you supply them;
• you are paying GST on your own inputs and would rather claim it than absorb it;
• a marketplace or client requires a GSTIN as a condition of onboarding;
• you expect to cross the threshold soon and would rather not deal with the stock-credit timing question later.

The cost is that compliance starts immediately and in full. Returns fall due every period whether or not you traded, late fees accrue on nil returns, and — since the three-year bar — unfiled returns can become permanently unfilable. Voluntary registration taken lightly is how a dormant registration turns into a demand years later.

What starts the day you are registered

Registration is the beginning of an obligation, not the end of a task:

• Tax invoices must be issued in the prescribed form, with your GSTIN.
• GSTR-1 and GSTR-3B fall due from the first period — monthly, or quarterly under QRMP where eligible.
• ITC-01 should be filed within 30 days if you are claiming the stock credit.
• Monthly reconciliation against GSTR-2B begins, because credit turns on what your suppliers report rather than on your invoices — see input tax credit and GSTR-2B.
• Display of the registration certificate at the place of business, and the GSTIN on the signboard.

Where books also need to be set up rather than merely filed from, that sits alongside as accounting and bookkeeping.

Casual and non-resident taxable persons

A separate track under Section 27. Someone supplying occasionally in a state where they have no fixed place of business — an exhibition, a seasonal stall, a one-off contract — registers as a casual taxable person, for a limited validity, and must make an advance deposit of estimated tax at the time of applying. It is not the ordinary route and should not be treated as one.

Whether to register under the composition scheme instead is a different decision, and it turns on who your customers are rather than on turnover alone — see when the composition scheme helps and when it costs.

GST is not the only 30-day clock running when a business starts. Karnataka establishments carry their own, from commencement at the premises rather than from incorporation — see shops and establishments registration in Karnataka.

Registration procedure has been changing quickly: the biometric step became universal by an interim court order on 8 September 2026 that may yet be varied, and the 57th GST Council on 7 October 2026 is expected to take up a faster route for larger applicants. Thresholds turn on the nature and place of supply. This note sets out the general position; whether registration is required in a particular case, and from what date, should be confirmed against the facts before applying.