GST for businesses: the practical basics

If you sell goods or services in India and cross the registration thresholds — or need registration for other reasons such as inter-state taxable supply, e-commerce marketplace listing, or voluntary opt-in — GST becomes part of how you bill, file, and reconcile. This page is a field guide for small businesses and freelancers, not a compliance manual.

Who needs to register (high level)

Turnover thresholds vary for goods vs services and for special-category states. A business supplying goods with aggregate turnover above 40 lakh (20 lakh in some states) generally needs registration. For services, the threshold is 20 lakh (10 lakh in some states). Inter-state supply, e-commerce sellers, and input-service distributors have mandatory registration regardless of turnover in many cases.

Check the current thresholds on the GST portal or with your CA — they have been revised and differ by state. Voluntary registration before threshold is allowed and can be useful if you want to claim input credit on purchases.

Quote exclusive, print clear invoices

Many B2B sellers quote exclusive and show GST as separate lines. That keeps fee negotiations clean — the client sees your fee and the government's tax as distinct items. B2C retail often shows inclusive stickers on products. Pick a house style and stick to it so your team does not mix modes on the same SKU.

A clean invoice shows: your GSTIN, client's GSTIN (if B2B), invoice number and date, HSN/SAC codes, taxable value per line, GST rate per line, CGST/SGST or IGST split, and total. Missing fields cause credit rejection for your client and notices for you.

Recheck any draft total with the GST calculator until your billing tool (Tally, Zoho Books, ClearTax) is trusted.

Rate master is sacred

Wrong HSN/SAC rate is a slow-burning problem. You bill 18% on a product that should be 12%, and the mismatch surfaces months later in GSTR reconciliation. Keep a rate master spreadsheet or locked fields in billing software. Review it when budgets revise slabs — July 2017 launch rates are not today's rates.

See GST slabs for a plain overview. For classification disputes, your CA and the GST tariff search are the authority.

CGST/SGST vs IGST

Place of supply drives the split. Sell within Maharashtra to a Maharashtra buyer → CGST + SGST. Sell from Maharashtra to a Karnataka buyer → IGST. Your software should handle this from GSTINs and place-of-supply fields. Mentally, intra-state ≈ CGST+SGST, inter-state ≈ IGST, same total tax for the same rate in the simple case.

Wrong place-of-supply selection is a common error for service businesses with remote clients. A Delhi consultant serving a Mumbai client may need IGST, not CGST/SGST.

Input tax credit is not automatic profit

Credit depends on eligibility, supplier compliance (did they file GSTR-1?), matching invoices in GSTR-2B, and timely return filing. A calculator that splits tax on an invoice does not tell you whether you can claim it. If your supplier has not filed, your credit is blocked until they do.

Budget working capital assuming 1–2 month delays in credit realisation. Small businesses often feel cash-crunched in the first year of GST registration because tax is collected immediately but credit flows lag.

Composition scheme — simpler, but limited

Small businesses below a turnover ceiling can opt for composition scheme: pay tax at a flat rate on turnover, file quarterly, and skip detailed invoice GST breakup. The trade-off: no input tax credit, no inter-state supply, and a "composition taxable person" label that some B2B clients dislike.

Composition works for local B2C — kirana, small eateries, local traders. It usually fails for freelancers serving corporate clients who need GST credit.

Freelancers and consultants

Once registered, add GST on taxable services at the right SAC rate — often 18% for IT, consulting, and professional services, but verify for your specific SAC. Show GSTIN on invoices. If a client insists on "all-inclusive 50,000", back-solve with inclusive mode so you still know the tax component is 7,627 at 18%, not 9,000.

Walkthrough: how GST is calculated. Inclusive vs exclusive: GST inclusive vs exclusive.

E-invoicing and e-way bills

Larger businesses must generate e-invoices with IRN (Invoice Reference Number) through the government portal. Thresholds have been lowered over time. E-way bills are required for goods movement above specified values. If you are a small freelancer billing services only, e-invoicing may not apply yet — but check the current turnover threshold.

When to call a CA

Registration choice (regular vs composition), LUT for exports, reverse charge on imported services, e-invoicing thresholds, notice replies, and annual reconciliation. Use Kalkulator.in for arithmetic; use a professional for positions and filings.

Hub page: GST calculator guide.

Monthly compliance rhythm

Even with clean billing maths, set a monthly rhythm: issue invoices with correct rates, file GSTR-1 by the due date, reconcile GSTR-2B against purchases, and pay liability through GSTR-3B. The calculator helps at invoice time; compliance software helps at month-end.

Disclaimer: Not tax advice. Rules and thresholds change with notifications. Verify with a qualified tax professional and official GST resources.