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OEM approves a retroactive price increase (say 3.5% effective three months back). The supplier has already invoiced and often been paid for hundreds of despatches in the intervening period. Section 34 CGST requires a supplementary debit note for the price differential on each despatch; GSTR-1 must reflect it; the OEM's ITC and the supplier's 194Q TDS must reconcile.
Extract every original invoice raised to the OEM between the revision effective date and the approval date. Multiply the taxable value of each invoice by the differential percentage. Generate one debit note per original invoice referencing the original invoice number and date under Rule 53. Aggregate the DNs into a differential register. Match the register to the OEM's price revision letter (aggregate control), to GSTR-1 Table 9B lines filed in the DN month, and to Form 26AS 194Q entries. Reconcile the OEM's payment against the DN aggregate net of 194Q TDS.
Retroactive period start date (revision effective date), retroactive period end date (approval date or first invoice at new price), price differential percentage, GST rate on underlying supply (28% for most auto components), TDS 194Q rate (0.1%), aggregate purchase threshold flag (₹50 lakh crossed in FY), 180-day ITC clawback trigger for the OEM.
Debit note register with one row per original invoice: original invoice number, date, taxable value, differential percentage, differential taxable value, differential GST, differential total, DN number, DN date, GSTR-1 amendment period, OEM ITC eligible month, payment status, 194Q TDS deducted. Aggregated by OEM plant, HSN, and GSTR-1 return period.
Retroactive price revisions are a structural feature of Indian auto component supply. OEMs and Tier-1 buyers negotiate annually or bi-annually, and the revised price is often approved months after the effective date. In the intervening period, the supplier has invoiced at the old price, and the OEM has paid — or in many cases part-paid, with retention. When the revised price is approved, the supplier must reach back into the invoice ledger and issue a supplementary debit note for every despatch that fell in the retroactive window.
For a large Tier-1 supplier delivering to a single OEM plant, a three-month retroactive window can span 200 to 400 individual despatches. Each despatch generated an original tax invoice, each of which must now be paired with a proportional debit note. This is not a bulk adjustment — Rule 53 of the CGST Rules requires each debit note to reference the original invoice number and date. Aggregation happens only at the reporting layer, not at the instrument layer.
This article walks the reconciliation between the original invoice ledger, the differential debit note register, GSTR-1 amendment lines, ITC visibility on the OEM’s GSTR-2B, and the 194Q TDS trail on Form 26AS.
The reconciliation in one paragraph
For each original invoice raised to the OEM between the price revision effective date and the approval date, the supplier calculates the differential taxable value, generates a supplementary debit note under Section 34(3) of the CGST Act, and reports it in Table 9B of GSTR-1 for the month of DN issuance. The debit note aggregate must tie to the OEM’s price revision letter — that is the primary control total. The differential GST flows to the supplier’s output tax and, once uploaded, appears in the OEM’s GSTR-2B for ITC. The differential net amount is billed to the OEM, subject to 194Q TDS at 0.1% at the payment stage. The reconciliation therefore has four tie-outs: (1) DN register aggregate equals price revision letter, (2) DN register equals GSTR-1 Table 9B for the DN month, (3) DN GST equals the incremental ITC line the OEM sees in GSTR-2B, and (4) DN payment received net of TDS equals the amount in Form 26AS 194Q for that quarter.
What retroactive OEM price increases look like in India
The commercial pattern is consistent across the sector. An OEM finance team — Tata Motors, Mahindra & Mahindra, Maruti Suzuki, Hyundai India, or Ashok Leyland — negotiates a price revision with the supplier commercial team based on input cost movements (steel, aluminium, semiconductors, energy). The negotiation runs longer than the effective date, either because raw material index formulas need to be finalised or because the OEM’s purchasing committee has monthly cadence and the item slips a cycle.
A Tier-1 forging supplier — illustratively Bharat Forge — supplying crankshafts to Tata Motors under an annual rate contract may see the following sequence. The rate contract has a raw-material pass-through clause that triggers when the SIMA steel index crosses a threshold. The index crosses in early April. The formal price revision request is submitted mid-May. The Tata Motors purchasing committee approves on 15 July, backdated effective 1 April. In the intervening 106 days, Bharat Forge has raised roughly 300 despatch-linked invoices for the Pantnagar and Sanand plants combined.
The same pattern applies at Tier-2. A Tier-2 forging or casting supplier — illustratively Sundram Fasteners or Rico Auto — with a similar pass-through clause to a Tier-1 buyer sees the equivalent cascade, sometimes with the additional complexity that the Tier-1 buyer’s own retroactive revision from the OEM triggers a matching retroactive revision to Tier-2. Suppliers such as Endurance Technologies, Motherson Sumi (Samvardhana Motherson), Uno Minda, Sona BLW, Amara Raja Batteries, and ZF India all operate under similar rate contract mechanics with the major OEMs.
The reconciliation problem is the same at every level: many despatches, one revision letter, tight tolerance on GST and TDS trail.
The regulatory overlay
Three regulatory regimes converge on the retroactive DN.
Section 34(3) CGST Act. Where the taxable value or tax charged in a tax invoice is found to be less than the taxable value or tax payable in respect of the supply, the supplier shall issue a debit note. This is the statutory basis for the supplementary invoice. Section 34(4) fixes the tax period of the debit note as the period in which the DN is issued, not the period of the original invoice.
Rule 53(1A) CGST Rules. The debit note must contain: name/address/GSTIN of supplier and recipient, nature of the document (“debit note”), a consecutive serial number, date of issue, serial number and date of the corresponding tax invoice, taxable value and tax charged on the differential, and signature of the authorised representative. The reference back to the original invoice is what makes many-to-one aggregation impossible at the DN layer — you cannot issue one DN referencing 300 original invoices.
GSTR-1 Table 9B. Amendments to previously reported credit/debit notes are reported in Table 9B. Fresh debit notes issued in the current period against invoices reported in earlier periods go into Table 9 (B2B debit/credit notes) with the linked original invoice details. The differential tax flows through the supplier’s output tax liability and, once GSTR-2B is generated for the OEM in the same period, becomes ITC-eligible for the OEM.
Section 194Q (Sl. 8 / payment code 1031 under the 2025 code set). The OEM, being a buyer whose turnover exceeds ₹10 crore, must deduct TDS at 0.1% on aggregate purchases from a single supplier exceeding ₹50 lakh in the financial year. The differential value on the DN adds to the aggregate purchase. TDS is deducted at the time of payment of the DN or credit to the supplier’s account, whichever is earlier.
Ind AS 115 variable consideration. Under paragraph 50 of Ind AS 115, the transaction price includes variable consideration that is expected to be received. A retroactive price revision changes the estimate of variable consideration. The cumulative catch-up is booked to revenue in the reporting period of approval.
Second proviso to Section 16(2) CGST. If the OEM does not pay the DN amount to the supplier within 180 days from the DN date, the incremental ITC claimed on the DN reverses proportionately to the unpaid portion. This is the same 180-day rule that applies to the original invoice, and the DN inherits its own separate 180-day clock. Refer to CBIC clarification 170/2021-GST and the Suncraft Energy line of case law confirming proportional (not full) reversal.
A worked example — illustrative numbers
An illustrative Tier-1 supplier, Bharat Forge, supplies crankshafts to Tata Motors’ Sanand plant under a rate contract. The steel pass-through clause triggers in April 2026. Tata Motors approves a 3.5% price increase on 15 July 2026, retroactive to 1 April 2026.
During the retroactive window (1 April to 14 July), Bharat Forge raised 300 tax invoices to Tata Motors Sanand, aggregating to ₹42 crore in taxable value. All despatches are 28% GST. All invoices have been either paid or part-paid by Tata Motors (some are in the 60-day payment cycle and unpaid on 15 July).
Step 1 — Extract the underlying despatch ledger. Filter the tax invoice register for GSTIN of Tata Motors Sanand, plant code, and invoice date between 1 April 2026 and 14 July 2026. Result: 300 invoices, ₹42 crore taxable value, ₹11.76 crore GST, ₹53.76 crore gross.
Step 2 — Compute the differential. 3.5% of ₹42 crore = ₹1.47 crore differential taxable value. 28% GST on ₹1.47 crore = ₹41.16 lakh differential GST. Gross differential = ₹1.8816 crore. This is the control total that must match the price revision letter.
Step 3 — Generate one DN per original invoice. 300 DNs, each referencing its original invoice number and date under Rule 53. The DN taxable value is 3.5% of the original taxable value, GST is 28% of the DN taxable value. All DNs are dated 20 July 2026 (five working days after approval, allowing time for ERP setup and DN numbering series).
Step 4 — Report in GSTR-1 for July 2026. All 300 DNs go into Table 9 of GSTR-1 filed on 11 August 2026, with linkage to the original invoice period (which spans April, May, June, and part of July). Tata Motors sees the aggregate ITC line in GSTR-2B for July 2026, generated on 14 August 2026.
Step 5 — TDS 194Q on the differential. Assume Tata Motors has already crossed the ₹50 lakh 194Q threshold with Bharat Forge in FY 2026-27. On the differential of ₹1.8816 crore gross, TDS at 0.1% on the taxable value component = 0.1% of ₹1.47 crore = ₹14,700. This is deducted at the time of payment or credit. It appears on Bharat Forge’s Form 26AS under section 194Q for Q2 FY 2026-27 (July–September quarter). Payment code on the TDS challan is Sl. 8 / 1031 under the 2025 code set.
Step 6 — Payment reconciliation. Tata Motors pays the DN aggregate on 15 September 2026 (assume 45-day payment cycle from DN date). Payment = ₹1.8816 crore minus ₹14,700 TDS = ₹1.88 crore net. Bharat Forge reconciles: (a) bank credit UTR to DN register aggregate, (b) 194Q entry on Form 26AS to TDS deducted at source per DN payment advice, (c) DN register aggregate to GSTR-1 Table 9B filed for July 2026.
Illustrative — actual differential percentage, GST rate, and TDS threshold behaviour depend on the specific rate contract, HSN, and cumulative FY purchases. Real values will differ; the reconciliation structure remains the same.
Common reconciliation breakages
Five recurring breakages appear in retroactive DN aggregation.
Missed despatches in the retroactive window. The extraction filter on the tax invoice register must match invoice date (or despatch date, depending on rate contract wording) against the retroactive window. Suppliers who filter on posting date rather than despatch date miss late-cutoff despatches that were physically shipped in the window but invoiced in the next accounting period. The control total against the price revision letter catches this only if the letter itself is aggregated by physical despatch schedule.
Wrong original invoice number on the DN. Rule 53 requires the DN to reference the original tax invoice number and date. Manual DN generation using a template that pulls from the sales register is fragile at 300-row scale. Errors here mean the OEM’s AP team rejects the DN because it cannot match to their PO or GRN. Automated aggregation with strict foreign-key linkage from DN to invoice is the only reliable approach.
Table 9B misreporting in GSTR-1. Some ERP GSTR-1 generators drop the linkage to original invoice period when the DN falls into a different quarter than the original invoice. This shows up as a mismatch when the OEM’s GSTR-2B ITC line lands in a different period than expected. Fix: manually verify Table 9B linkage for retroactive DNs before filing.
194Q not deducted on the differential. OEM AP systems that pre-configure 194Q at the original invoice stage and mark the invoice “TDS deducted” sometimes fail to re-evaluate the 194Q threshold at the DN payment stage. If the differential adds ₹1.47 crore to the aggregate purchase and pushes it further above the ₹50 lakh threshold, TDS at 0.1% applies on the differential too. Missed 194Q on the DN causes a mismatch in Form 26AS reconciliation.
Retention interaction. If the OEM has withheld 5-10% retention on the original invoices, the retention on the differential is often overlooked. The DN gross of ₹1.8816 crore may be part-paid at ₹1.7852 crore with ₹9,408 retention held, plus TDS. Retention is not a short-payment — see the companion article on retention debit treatment — but the ITC clock (180 days) and the AP reconciliation both need to record the retention explicitly.
How a reconciliation platform handles this
A reconciliation platform ingests three primary streams: the original tax invoice register (from ERP sales module), the DN register (either generated by the same ERP or by an external DN tool), and the GSTR-1 filed return. For 194Q verification, it also ingests Form 26AS entries by quarter.
The core reconciliation loop pairs each DN row to its underlying original invoice using the Rule 53 reference field, aggregates DNs into a control total, and compares four numbers: (a) DN register aggregate, (b) price revision letter total, (c) GSTR-1 Table 9B filed amount for the DN month, (d) GSTR-2B ITC line that the OEM sees. Any variance above a configurable threshold — typically ₹100 or 0.01% of aggregate — is flagged.
The platform also runs the 180-day clock forward from the DN date and produces an ITC clawback risk report for the OEM: if the DN is not paid within 180 days, the ITC on the unpaid proportion reverses. The report flags DNs approaching the boundary at 150 and 165 days.
For 194Q, the platform tracks the aggregate purchase value per supplier per financial year and cross-checks Form 26AS entries against the DN payment advice. Any 194Q entry missing on Form 26AS relative to the DN payment record is flagged for follow-up with the OEM’s TDS cell.
Auto Tier-1 and Tier-2 suppliers running annual rate contracts across multiple OEMs typically see three to eight retroactive revision events per year, each with 100 to 500 underlying despatches. The reconciliation infrastructure that manages this at scale is the same infrastructure that handles regular monthly reconciliation software India and GST reconciliation software workflows — the retroactive DN event is a variant of the standard invoice-to-return-to-payment reconciliation, with the additional layer that one control total (the revision letter) governs many individual instruments.
Related reading
- Rejection debit after invoice paid — Section 34 credit note
- Retention debit 5% is not a short payment
- ITC clawback 180-day boundary — Section 16 second proviso
- ITC clawback partial payment — proportional treatment
- MSME 45-day payment compliance tracker
- TDS payment code 1031 (Sl. 8) — Section 194Q purchase of goods
- Automate GST IMS reconciliation India
- Bosch SupplyOn portal ASN reconciliation
- Debtors–creditors reconciliation India
Content authored by practitioners with experience at Amazon India, Intuit QuickBooks, and the Tata Group. Meet the team →
- ▸ CGST Act, Section 34 — Section 34(3) — debit note where taxable value or tax charged in a tax invoice is found to be less than the taxable value or tax payable
- ▸ CGST Rules, Rule 53 — Rule 53(1A) — content requirements for revised tax invoices and debit notes, including reference to original invoice number and date
- ▸ GSTN — GSTR-1 filing instructions — Table 9A (B2B amendments) and Table 9B (credit/debit notes amendments) — how to report supplementary invoices in later-month returns
- ▸ Income Tax Act, Section 194Q (successor code Sl. 8 / 1031 under 2025 codes) — TDS at 0.1% by buyer on purchase of goods above ₹50 lakh in a financial year — payment code 1031 under the 2025 code set
- ▸ Ind AS 115 — Revenue from Contracts with Customers — Variable consideration — price revisions require reassessment of transaction price and cumulative catch-up adjustment