Use the exception only when quantity is unknown at removal
Section 31 of the CGST Act sets the normal invoicing rule for taxable goods involving movement. Rule 55(1)(a) allows a delivery challan in lieu of an invoice at removal for supply of liquid gas where the quantity is not known at that point. When goods are transported for supply but a tax invoice could not be issued at removal, Rule 55(4) requires the supplier to issue the invoice after delivery. This is not a general permission to defer invoicing for all bulk goods, all tanker deliveries or for month-end convenience.
Read the applicable text: CBIC CGST Act, section 31 CBIC CGST Rules, Rules 55 and 138 GST Portal advisory, documents issued in Table 13.
Document the dispatch before the tanker moves
Use a serial number of up to 16 characters. Include the date, consignor and consignee names and addresses, their GSTIN or UIN where applicable, HSN and description, and the quantity (provisional if the exact quantity is unknown). Include taxable value, the applicable tax rate and amount for supply, place of supply for inter-State movement, and signature. For a supply of goods, mark the three copies as original for the consignee, duplicate for the transporter and triplicate for the consignor. Rule 55(3) connects the movement to Rule 138; determine the actual e-way bill obligation and any applicable exception before release. A delivery challan is not an automatic exemption.
Build a measured delivery bridge
Use the unit and metering basis specified in the contract, such as calibrated net weight or the supported meter difference. Link vehicle, customer, seals, measurement time, delivery evidence and discrepancies to the challan. A single tanker route may have multiple drops; capture each recipient’s quantity without treating gross load as that recipient’s delivery. Maintain the provisional quantity and value as historical evidence and record actual delivery separately.
Issue the tax invoice and keep the two records linked
Apply the confirmed quantity, legally supported value and applicable GST classification and rate to the invoice. The examples use hypothetical rates and do not classify a particular gas. Retain the challan as the movement document; report the actual invoice in the applicable outward supply records. Where Table 13 of GSTR-1 or GSTR-1A applies, report the issued delivery challan in its own document series and the invoice in the relevant invoice series. If an invoice has already been issued and the value or quantity is then found wrong, assess the applicable correction route; do not replace a completed invoice simply by altering the historical challan.
Separate shortages from billable quantities
Compare load, delivery, returns and verified loss. Measure each component independently; establish how the contract prices actual delivery and resolve any stock loss or tax consequence separately. Where goods were transported in known batches under an already determinable supply, examine Rule 55(5) on its own terms; it is a different use case from unknown liquid-gas quantity.
Six worked illustrations
All facts and amounts are fictional. Calculations illustrate the stated assumptions, not a predetermined legal outcome.
Illustrative example 1: Provisional estimate versus actual delivery
The dispatch estimate is 1,200 kg and measured delivery is 1,170 kg at an illustrative ₹40 per kg. The taxable invoice value is ₹46,800 on those assumptions, ₹1,200 below the provisional ₹48,000.
Illustrative example 2: Higher confirmed delivery
Estimated delivery is 800 kg and the calibrated meter shows 825 kg. At ₹52 per kg, actual value is ₹42,900 versus ₹41,600 provisional, a ₹1,300 difference.
Illustrative example 3: Gross and tare
For a single complete delivery, the same vehicle weighs 16,840 kg before discharge and 12,460 kg after discharge on a calibrated weighbridge. Assume no other weight changes and that the contract accepts this measure. Delivered quantity is 4,380 kg; at ₹30 per kg the taxable value is ₹1,31,400.
Illustrative example 4: Two recipient drops
The tanker starts with 3,000 kg, drops 1,250 kg and 1,100 kg and returns with 640 kg. A 10 kg difference remains to investigate. At ₹42 per kg the two supported delivered values are ₹52,500 and ₹46,200.
Illustrative example 5: Illustrative invoice tax
Assume inter-State supply of 1,500 kg at ₹48 per kg with a stipulated illustrative 18% IGST rate. Taxable value is ₹72,000, IGST is ₹12,960 and gross invoice is ₹84,960. Verify the actual classification and rate separately.
Illustrative example 6: Disputed measurement isolated
A supplier records 1,020 kg but signed evidence presently supports 1,000 kg. At ₹35 per kg, ₹700 of potential value requires resolution; ₹35,000 is supported by the signed measurement alone.
Ten-step verification table
| Step | Action | Evidence |
|---|---|---|
| 1 | Confirm exception eligibility | Gas description and reason quantity was unknown at removal |
| 2 | Review the measurement terms | Contract unit, accepted method and calibration |
| 3 | Issue challan before dispatch | Dated numbered document and required particulars |
| 4 | Control copies and driver papers | Consignee, transporter and consignor records |
| 5 | Assess e-way bill before movement | Applicable Rule 138 evidence and vehicle details |
| 6 | Capture measurement at delivery | Meter or weighbridge slips and timestamps |
| 7 | Reconcile all drops and returns | Route log and opening-to-closing quantities |
| 8 | Compute actual taxable value | Approved quantity and valuation evidence |
| 9 | Raise and link the tax invoice | Invoice record and challan reference in working |
| 10 | Close reporting exceptions | Document series, returns and discrepancy sign-off |
Sixteen practitioner FAQs
1. May an ordinary liquid use this rule just because it is carried in a tanker?
Rule 55(1)(a) is specifically for supply of liquid gas with quantity unknown at removal.
2. Is a known truck capacity the same as known supply quantity?
No. Establish the actual contract quantity and dispatch facts.
3. Can estimated quantity be on the challan?
Yes, where exact supplied quantity is unknown; retain the basis of the estimate.
4. Can the challan omit provisional taxable details?
Review Rule 55(1)'s required particulars; unknown final quantity is not a blanket exemption.
5. Does the challan need a signature?
Signature is one of the listed particulars.
6. How many challan copies for supply?
Rule 55(2) provides three designated copies.
7. Is the challan the supplier's tax invoice?
No. Complete the tax invoice after delivery in the covered case.
8. Is an e-way bill automatically unnecessary?
No. Review Rule 138 and the facts independently.
9. Can a seller aggregate all customers on one final invoice?
Do not combine distinct recipients merely because the tanker route is shared.
10. What if the contractual unit differs from the scale reading?
Use a documented, contract-consistent conversion; preserve the original measurement.
11. Can a returned quantity be billed as delivered?
Check the actual delivery and contractual obligation; preserve the return record separately.
12. How should a disputed meter reading be handled?
Record both readings and use the agreed resolution procedure before treating a disputed amount as final.
13. Does unknown quantity permit ignoring the tax period?
No. Review time of supply and applicable filing rules separately.
14. Can the challan be silently rewritten after delivery?
Preserve the issued record and link the final measured outcome.
15. Does a challan itself support the recipient's invoice-based credit claim?
Verify prescribed tax documents and the other credit conditions separately.
16. Does Rule 55(5) give the same invoice sequence?
No. It prescribes a complete invoice before the first consignment for its specified cases.
Official sources
CBIC CGST Act, section 31 CBIC CGST Rules, Rules 55 and 138 GST Portal advisory, documents issued in Table 13