GST Education

GST Registration & Invoice Rules: What New Businesses Must Know

When you cross the GST registration threshold or voluntarily register, several new obligations kick in immediately — and invoice compliance is the most visible one. This guide explains the registration thresholds, what invoice rules apply from day one, and what mistakes new registrants commonly make.

By Arjun Sharma · GST & Tax Compliance Specialist · Published Apr 24, 2026 · Updated Apr 25, 2026 · Reviewed for GST accuracy

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GST Registration Thresholds (2026)

Supplier Type	State	Threshold
Goods + Services	Most states	₹40 lakh for goods, ₹20 lakh for services
Goods + Services	Special category states	₹20 lakh for goods, ₹10 lakh for services
E-commerce seller	Any	Mandatory (no threshold)
Interstate supplier	Any	Mandatory (no threshold)
Casual taxable person	Any	Mandatory before starting

Important

Special category states include Arunachal Pradesh, Assam, Jammu & Kashmir, Himachal Pradesh, Uttarakhand, Manipur, Meghalaya, Mizoram, Nagaland, Sikkim, and Tripura.

What Changes on the Day You Register for GST

From your effective registration date:

You must issue Tax Invoices (or Bill of Supply if applicable) for all taxable supplies
You must collect GST from buyers and remit it to the government
You are eligible to claim Input Tax Credit (ITC) on business purchases
You must file monthly/quarterly returns (GSTR-1, GSTR-3B)
You cannot issue invoices for supplies made before the registration date

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Voluntary GST Registration — When and Why

You can register for GST even if your turnover is below the threshold. Reasons to voluntarily register:

Clients require your GSTIN for ITC claims (common for B2B)
You want to claim ITC on your own business purchases
You plan to supply interstate (mandatory threshold)
Competitive positioning — appearing more "formal"
Access to government tenders (often require GST registration)

Invoice Rules for New Registrants

Key invoice rules to know from your first day of registration:

Start invoice numbering from 1 (or 001) on your registration date
Include your GSTIN on every invoice from the registration date
Determine correct tax type for each transaction (CGST+SGST or IGST)
HSN/SAC codes are mandatory — 4 digits for turnover under ₹5 crore
Report all invoices in GSTR-1 (monthly or quarterly, depending on your turnover)
File GSTR-3B on the 20th of each month to pay tax due

Invoice Rules Under Composition Scheme

Small businesses (turnover under ₹1.5 crore for goods, ₹50 lakh for services) can opt for the Composition Scheme. Key differences:

Aspect	Regular GST	Composition Scheme
Document issued	Tax Invoice	Bill of Supply
GST collected from buyer	Yes	No
Tax shown on document	Yes (CGST/SGST/IGST)	No
ITC to buyer	Yes	No
ITC claim for purchases	Yes	No
Returns	GSTR-1 + GSTR-3B	CMP-08 quarterly + GSTR-4 annual

Common Mistakes New Registrants Make

Issuing invoices before GSTIN is assigned (use "GST Registration Pending" only in exceptional cases, with care)
Not restarting invoice numbering at the beginning of each financial year
Charging GST on exempt supplies (e.g., basic food items)
Applying wrong tax type: CGST+SGST for interstate, or IGST for intrastate
Missing GSTIN of the buyer on B2B invoices
Delaying GSTR-1 filing — late fees apply from day one

FAQs

When does GST registration take effect?

GST registration is effective from the date of application if the liability to register arises from that date. In practice, the effective date is shown on your GST registration certificate.

Can I charge GST before my GSTIN is issued?

Technically no. Your GSTIN must appear on every invoice. If your GSTIN is delayed, wait for it before issuing tax invoices. You can raise a pro-forma invoice during the gap if needed.

Do I need separate GST registration for each state?

Yes. If you have business operations (offices, warehouses, agents) in multiple states, you need a separate GST registration for each state.

What is the penalty for late GST registration?

If you were required to register but did not, all supplies made during that period are treated as tax-evaded. You may face a demand for unpaid tax plus interest (18% p.a.) plus penalty.

Can I deregister if my turnover falls below the threshold?

Yes. You can apply for cancellation of GST registration if your turnover consistently falls below the threshold. However, ITC claimed during registration must be reversed on stock held at the time of cancellation.

Why Businesses Stop Using Excel for GST Invoices

Manual GST calculation mistakes

One wrong CGST/SGST split or a misapplied rate triggers notices and ITC denial for your buyer.

Slow invoice creation

Copying last month's Excel file, updating dates, recalculating — 20 minutes for what should take 30 seconds.

Formatting breaks on every device

Excel invoices look different on every printer and PDF converter. Clients complain about unreadable layouts.

No easy sharing or payment link

Sending PDFs over WhatsApp with no way for clients to pay directly slows down collections.

Incorrect tax type (IGST vs CGST+SGST)

Excel can't auto-detect intra vs inter-state supply. Wrong tax type = ITC rejected for your buyer.

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Disclaimer: The information in this article is for general informational purposes only and does not constitute professional tax, legal, or financial advice. GST rules and rates are subject to change. Consult a qualified CA or tax professional before making compliance decisions.

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