GSTIN
The 15-character registration number the GST Network issues to a registered person. The first two digits identify the state of registration, and the number is tied to the business's PAN, which is why a change in the business's legal structure can mean a change of GSTIN.
Why it matters in practice. It is how a B2B invoice is addressed, and a wrong or missing GSTIN moves a tax problem onto your customer instead of preventing it. It is a registration identity: it is not a tax rate, and it is not a signal that a return has been filed.
Often confused with Tax invoice particulars, HSN and SAC, Tax invoice.
HSN and SAC
The classification codes for what is being supplied: HSN, from the Harmonised System of Nomenclature, for goods, and SAC, the Services Accounting Code, for services. The code says what the item is; it is a separate decision from the rate applied to it.
Why it matters in practice. The code and the rate are separate decisions that get collapsed into one, and the right rate on the wrong code is still a wrong invoice. How many digits a particular taxpayer must carry is a requirement that varies — settle that for your own business with your chartered accountant rather than from a summary.
Often confused with Taxable value, GSTIN, Tax invoice particulars.
CGST and SGST
The two components of GST that apply to a supply within one state: Central GST and State GST. Each is levied at half the applicable rate and the two are collected together on the same invoice, rather than being two separate taxes.
Why it matters in practice. Which split applies depends on where the supply is, so getting the place of supply right is what determines whether the invoice is split or carries IGST. An invoice with the wrong component is not a formatting mistake.
Often confused with IGST, Place of supply, Taxable value.
IGST
Integrated GST: the single component levied on supplies between states and on imports, at the full applicable rate. It is collected by the Centre and is subsequently shared with the states.
Why it matters in practice. IGST on an invoice is not a detail — it changes what the customer needs in order to take a credit. Whether a particular sale is inter-state is a place-of-supply question, and for many categories of supply the answer is not simply the delivery address.
Often confused with Place of supply, CGST and SGST, Taxable value.
Place of supply
The location used to determine the tax treatment of a supply — the point at which the law treats the supply as having occurred. The rules for determining it differ by category of supply, and for services it is frequently neither the supplier's address nor the customer's.
Why it matters in practice. This single determination decides whether the invoice carries a CGST and SGST split or IGST. Taking it from the shipping address is the shortcut that produces a tax invoice a customer's accountant cannot use, and the cost of fixing it later falls on both sides.
Often confused with IGST, CGST and SGST, E-way bill.
Taxable value
The value of the supply that GST is calculated on: the consideration for it, adjusted for the items the law requires to be included in or excluded from that value. The invoice total is the taxable value plus the tax calculated on it.
Why it matters in practice. Discounts, freight, and other charges can affect what belongs in the value of supply, and those rules are specific and have changed more than once. Settle your treatment with your chartered accountant and then configure it once, rather than deciding it afresh on every invoice.
Often confused with CGST and SGST, Invoice, Input tax credit.
Tax invoice particulars
The set of particulars a tax invoice must carry. Section 31 of the CGST Act is the base provision for issuing tax invoices, and the particulars for the general case are set out in the CGST Rules — Rule 46 is the provision most often cited.
Why it matters in practice. This list is what turns a receipt into something a customer can act on. Software should make these fields structured and reviewable; what your own invoices are required to carry is a question for your chartered accountant, and the rules can be amended.
Often confused with Tax invoice, HSN and SAC, GSTIN.
E-invoice and IRN
E-invoicing means reporting an invoice to the Government's e-invoice system, which generates an Invoice Reference Number (IRN) and a signed QR code for that document. Whether a particular taxpayer is required to do this depends on the notifications that apply to them, and the official portal is where to look.
Why it matters in practice. Treat it as a capability to be ready for rather than a number to plan against. What an enablement listing on a portal does or does not settle is a legal question for your chartered accountant, not a software question — and structured, exportable invoice data is the part worth getting right either way.
Often confused with Tax invoice, E-way bill, Invoice.
E-way bill
A document generated through the GST e-way bill system carrying details of goods being moved, for the supplies and values it applies to. Where it is required, it is generated before the goods move, and it is a completely separate obligation from e-invoicing.
Why it matters in practice. Moving goods and reporting a sale are distinct requirements, and conflating them is common. Applicability, any value threshold, and validity come from notifications that change — check the current position for your own supplies rather than relying on a summary.
Often confused with E-invoice and IRN, Invoice, Place of supply.
Reverse charge
A mechanism under which the liability to pay GST on a supply shifts from the supplier to the recipient, in the cases the law specifies. Both parties retain their own obligations; what moves is who pays.
Why it matters in practice. It applies to specific notified categories, and it changes who is expected to issue the tax invoice. Treating a supply as reverse-charge when it is not, or missing it when it is, is a real liability rather than a paperwork error.
Often confused with Input tax credit, Tax invoice particulars, E-invoice and IRN.
The credit a registered person may take for GST paid on inward supplies, subject to the conditions the Act places on it — including documentation, the use the credit is put to, and the returns filed. It is a credit set against your own output tax, not a refund of the cost of the purchase.
Why it matters in practice. It is the reason the particulars on your invoices matter to your customers: an invoice that cannot support a claim becomes a commercial problem for you at renewal. Whether a particular expense is eligible is a question for your chartered accountant.
Often confused with Reverse charge, Taxable value, GSTIN.
A commercial document declaring an intention to supply at a stated value, typically issued before or at the start of a supply — commonly to request an advance. It is not defined in the CGST Act, and it is not the tax invoice the Act requires for a taxable supply.
Why it matters in practice. The confusion is expensive because a proforma looks like an invoice and gets filed like one. Whether tax should be shown on a proforma, and in what form, is a point your chartered accountant should confirm for your business rather than a software default.
Often confused with Tax invoice, Tax invoice particulars, Taxable value.