Does a GST e-invoice contain everything needed to calculate emissions, and which fields matter?

Nearly, for goods. A GST e-invoice carries an HSN code on every line and usually a description, quantity and unit, which is most of what an activity-based calculation needs. It never gives the emission factor, and diesel, petrol, natural gas and grid electricity are outside GST, so their bills are not e-invoices.

The fields that matter, line by line

• HSN code (HsnCd): narrows the line to a material or fuel family and decides the likely scope. Mandatory on every e-invoice line.
• Product description (PrdDesc): picks the exact item within the HSN heading, such as LPG against natural gas under 2711.
• Quantity (Qty) and unit (Unit, a GST Unique Quantity Code such as KGS, LTR, MTS or NOS): the activity data the factor multiplies.
• Taxable value (AssAmt): the rupee amount before GST, used only for a spend-based estimate when no quantity exists.
• Document date: puts the purchase in the right month and reporting year.
• Seller GSTIN: identifies the supplier for a Scope 3 supplier trail.
• IRN: a unique reference per invoice, useful to stop the same invoice being counted twice.

What an e-invoice does not tell you

• The emission factor. You still choose a published factor that matches the item and unit.
• Whether fuel was burnt, stocked or resold. A purchase is not the same as consumption.
• Mass, when the unit is NOS, PCS, BOX or OTH. Ten LPG cylinders in NOS need the cylinder size to become kg.
• Anything about services beyond a SAC code and an amount, so services stay spend-based.

Which purchases never come as e-invoices

Petrol, diesel, aviation turbine fuel and natural gas are outside GST, and grid electricity is exempt. Their bills carry no IRN and often no HSN code. These are usually the biggest Scope 1 and Scope 2 lines for an MSME, so they must come from pump slips, gas bills and discom bills.

LPG, coal, furnace oil and petroleum coke are under GST, so a supplier above the e-invoicing turnover threshold (aggregate turnover over Rs 5 crore) issues them as e-invoices. Small suppliers below the threshold issue ordinary tax invoices.

A practical rule for finance teams

1. Use e-invoices for goods purchases: take HSN, description, quantity and unit from each line.
2. Convert counts to mass or volume with a documented size, such as kg per cylinder or bag.
3. Take fuel and electricity from the source bills, since they sit outside the e-invoice system.
4. Use taxable value only for lines with no physical quantity, and label those spend-based.

Worked example: two fuel lines on one e-invoice

• Line 1: HSN 2711, commercial LPG, Qty 10, Unit NOS (19 kg cylinders)
• 10 x 19 kg = 190 kg; 190 x 2.98 kg CO2 per kg = 566.2 kg CO2
• Line 2: HSN 2710, furnace oil, Qty 5,000, Unit LTR
• 5,000 x 2.97 kg CO2 per litre = 14,850 kg CO2
• Total: 566.2 + 14,850 = 15,416.2 kg CO2, about 15.4 t, Scope 1 if burnt on site

Factors are IPCC 2006 defaults (furnace oil at an assumed 0.95 kg per litre). The cylinder size came from the description, not from the unit field.

What Senseible does here

Senseible reads tax invoices, including e-invoices, as PDFs or photos, and returns each line's HSN code, description, quantity and unit, leaving absent fields empty rather than guessed. It classifies by HSN first and applies a factor only when the unit fits. Where only spend is known, it can give a spend-based estimate, labelled as such.

• Carbon footprint from invoices
• GSTR-2B for carbon accounting?
• Invoice in litres, factor in kg
• Stop the same invoice counting twice

Sources: GHG Protocol Technical Guidance for Calculating Scope 3 Emissions (2013), Category 1, 2006 IPCC Guidelines, Volume 2 Energy

Last reviewed 2026-10-17. The e-invoice schema (INV-01), the turnover threshold and the list of goods outside GST are set by GSTN and the GST Council; recheck them each year.