Do I need GST registration?

₹40 lakh of aggregate turnover in a financial year for a supplier of goods only in most states, ₹20 lakh for services or a mix, and ₹10 lakh for both in Manipur, Mizoram, Nagaland and Tripura. Arunachal Pradesh, Meghalaya, Sikkim, Puducherry, Telangana and Uttarakhand kept the goods limit at ₹20 lakh (section 22(1) and Notification 10/2019-Central Tax). The checker applies the figure for the state you pick.

Not on turnover alone, but section 24 lists cases where it is compulsory from the first rupee: inter-state supply of goods, selling goods through a marketplace that collects TCS, being a casual or non-resident taxable person, having to pay tax under reverse charge, and acting as an agent for a registered person. If none of those applies, registration below the limit is voluntary under section 25(3).

For goods, yes in most cases (section 24(ix)). The one exception since 1 October 2023 is a seller who sells only within their own state, stays under the threshold, has a PAN, declares it on the GST portal and holds an enrolment number (Notification 34/2023-Central Tax). For services sold through a platform, the normal threshold applies (Notification 65/2017-Central Tax).

Not until you cross the threshold. Notification 10/2017-Integrated Tax exempts inter-state suppliers of services from compulsory registration until aggregate turnover reaches ₹20 lakh (₹10 lakh in the special-category states). Inter-state supply of goods, by contrast, needs registration from the first sale.

Aggregate turnover under section 2(6): all taxable, exempt, export and inter-state supplies of every business under the same PAN, across India, in the financial year, excluding the GST itself and inward supplies taxed under reverse charge. Exempt income and exports count towards the limit even though no tax is charged on them.

30 days from the day you became liable (section 25(1)). Apply within the 30 days and the registration is effective from that day (Rule 10(2)); apply later and it is effective only from the date of grant, so the tax on sales in the gap comes out of your margin, with interest at 18% (section 50) and a penalty under section 122.

FORM GST REG-01 asks for proof of the principal place of business: an ownership document for owned premises; the rent or lease agreement plus the landlord's ownership proof for rented premises; a consent letter plus the owner's ownership proof for premises used with permission. If you have no premises in the state, a commercial virtual office supplies the agreement, owner NOC and utility bill, and the officer may visit it (Rule 25).

Yes, under section 25(3), and once registered every provision of the Act applies to you: returns for every period including nil returns, tax on every taxable supply, and the late fees in section 47 if a return is missed. Register voluntarily when a customer, a marketplace or input credit makes it worthwhile, not merely because it is free.