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Indian Tier 1 auto-component suppliers face structural short-pays of 5-12% of monthly OEM billing through auto-debit mechanisms — FOMP warranty back-charges at 1-3% of billing, quality penalty deductions, JIT delivery shortage debits, line-stop charges, and tooling adjustments. GST credit-note timing under Section 34, Rule 37 ITC reversal at 180 days, and Section 393(1)(a) contractor TDS on subcontract job-work all overlay the settlement cycle, and a single OEM debit memo can hit four ledgers.
Reconcile every OEM payment against the cumulative billing run net of debit memos, classify each debit by reason code (FOMP, JIT shortage, quality penalty, line-stop, tooling, transport), tie each debit to the originating claim ID and underlying invoice, decide GST credit-note action within the Section 34 window, age unpaid short-pays against the 180-day Rule 37 ITC reversal clock, deduct Section 393(1)(a) code 1002 on subcontract job-work invoices, and maintain a Tier 1 to Tier 2 back-charge passthrough register so quality recoveries flow down the chain.
OEM customer master keyed by plant code and vehicle programme, debit-memo reason taxonomy with claim ID and link to source invoice, FOMP running account per OEM, GST credit-note workflow keyed to Section 34 30-November cutoff, Rule 37 ageing buckets at 60/90/150/180 days, Section 393(1)(a) vendor rate matrix with code 1002 default, JIT call-off schedule by part number with shortage tracking.
A daily OEM settlement view per Tier 1 customer showing billed vs paid vs debited amount with reason-coded variance, FOMP exposure aged by claim ID, GST credit-note action queue by approaching Section 34 cutoff, Rule 37 ITC-reversal risk register by short-pay age, monthly Section 393(1)(a) TDS challan tied to subcontract payments, and Tier 2 passthrough debit register linking each OEM back-charge to the recovery raised on the sub-tier supplier.
A Tier 1 brake-system supplier in Pune closes the June quarter and pulls the Maruti Suzuki settlement: ₹120 crore quarterly billing, ₹9.6 crore short-paid through auto-debit, ₹3 crore of which was raised as discrete debit notes for FOMP, JIT shortages, line-stop charges and quality penalties. The pattern is industry-wide. Any OEM Tier 1 settlement reconciliation India function that handles Maruti, Tata Motors, Mahindra & Mahindra, Hyundai or Toyota Kirloskar has to operate inside an auto-debit regime where the OEM deducts first and the supplier reconciles second.
Quick reference
| Item | Value |
|---|---|
| Typical OEM short-pay band | 5% to 12% of monthly billing |
| FOMP warranty back-charge range | 1% to 3% of trailing monthly billing |
| Net payment terms | 60 to 90 days from invoice for most Indian OEMs |
| GST rate (auto components) | 28% on most components; 18% on selected; 5% on EV |
| GST credit-note window | Section 34 — 30 November of next FY or annual return, whichever earlier |
| ITC reversal trigger | Rule 37 — 180 days from invoice date if unpaid |
| Subcontract TDS code | Section 393(1)(a) code 1002 (legacy 194C) |
| Purchase TDS code | Section 393(1)(k) code 1012 (legacy 194Q) |
How does the OEM auto-debit mechanism actually work
Indian OEMs run electronic settlement against the supplier’s running ledger. The supplier files the invoice through the OEM portal (Maruti’s eSCM, Tata Motors’ iCMS-style ledger, Mahindra’s vendor portal). For the billing period — typically a fortnight or a calendar month — the OEM aggregates all invoices, deducts every captured debit (FOMP claims raised in the period, JIT shortages logged at line, line-stop charges by hour, quality rejection slips, tooling amortisation credits, transport debits), and remits the net.
The supplier sees a single bank credit with an attached settlement statement listing every line. Reconciliation must immediately split the statement: which lines are clean invoice payments, which are reason-coded debits, and which require dispute action within a 30-day window before the debit becomes commercially final.
The seven debit categories
1. FOMP — Field-Originated Material Performance
A field warranty claim at an OEM dealer traces back to a specific part dispatched 4-18 months earlier. The OEM raises a FOMP debit citing the warranty claim ID, vehicle VIN range and technical service deduction analysis. Indian OEMs typically run FOMP at 1-3% of monthly billing. A Tier 1 holding 12 OEM customers and ₹400 crore annual revenue typically carries a 4-6% FOMP provision on the balance sheet — ₹16-24 crore — until each claim is closed or written back.
2. Quality penalty deductions
Beyond field warranty, OEMs penalise PPM (parts-per-million) defect rates exceeding the contractual target, line rejection rates, audit non-conformances, and ASES/QSB-audit findings. A part rejected at the OEM line returns on the next return-trip truck and triggers a quality debit equal to the part value plus a handling/rework fee.
3. JIT delivery shortage debit notes
When a supplier’s dispatched kanban falls short of the called-off quantity, the OEM either starts the line short or pulls from emergency reserve. The shortage debit covers the un-supplied quantity at the contracted part rate plus an expediting premium — often 2x the part value when the OEM has to airlift from an alternate plant.
4. Line-stop charges
If a shortage or quality issue causes an actual line stoppage, the OEM raises a line-stop charge by the hour. Indian OEMs encode line-stop rates in the commercial agreement — typically ₹1-5 lakh per hour depending on the vehicle programme and plant.
5. Tooling amortisation adjustments
When cumulative parts shipped on a programme exceed the contractual tooling-recovery cap, the over-recovery is credited back via a tooling adjustment debit on the next settlement.
6. Technical service deductions
OEM-resident engineers from quality, engineering and supply-chain teams visit supplier plants for audits, line trials and incident investigation. The OEM debits the supplier for engineer time at a contractual hourly rate when the visit is supplier-caused.
7. Transport debits
When the OEM arranges premium freight (airfreight, dedicated truck) to cover a supplier shortage, the freight differential is debited on the next settlement.
GST credit-note timing under Section 34
The OEM’s debit note is a commercial document — it triggers the auto-debit but does not itself reverse GST on the supplier’s books. The supplier must issue a GST credit note under Section 34 of the CGST Act to actually reduce the GST liability for the accepted debit. Section 34 imposes a hard timing window: the GST credit note must be issued by 30 November of the next financial year, or the date of filing the annual return, whichever is earlier. A debit raised in October 2026 against an FY 2025-26 invoice has until 30 November 2026 to be turned into a GST credit note; after that, the commercial recovery may still be possible but the GST liability stands.
For reconciliation, this means every accepted OEM debit triggers a credit-note action with a hard calendar deadline. A separate workflow ages disputed debits against the same deadline so disputes are resolved before the GST window closes.
Rule 37 ITC reversal at 180 days
Rule 37 of the CGST Rules requires the OEM to reverse ITC if the supplier is not paid within 180 days of the invoice date. For a Tier 1 whose Maruti invoice has been 12% short-paid and dispute is open, the OEM faces Rule 37 reversal at day 180 on the unpaid 12% — and OEMs do not absorb the reversal. They force settlement at day 150-170 by either releasing the disputed amount or demanding a supplier-issued credit note. Reconciliation at the Tier 1 must age every short-pay against the 180-day clock with action triggers at 60/90/150/180 days.
Section 393(1)(k) vs 394 Threshold Determiner
For Tier 1 suppliers issuing back-charges to Tier 2 vendors, determine whether Section 393(1)(k) purchase-of-goods TDS or Section 394 scrap TCS applies to each transaction line and at what threshold.
Open the Threshold Determiner →Section 393(1)(a) TDS overlay on subcontract job-work
A Tier 1 outsources heat treatment, electroplating, induction hardening, painting, machining and sub-assembly to a network of Tier 2 vendors. Every such payment attracts Section 393(1)(a) TDS at payment code 1002 — the successor to legacy Section 194C from 1 April 2026. Rate is 1% for individual/HUF, 2% for company/firm, with thresholds ₹30,000 per transaction and ₹1 lakh aggregate per FY. See Section 393 TDS new Income Tax Act reconciliation and TDS payment codes 1001-1092 India for the full code map.
Composite job-work invoices that include goods (returnable inputs, consumables) must be split — TDS applies only to the service component.
Worked example — ₹120 crore quarterly Maruti billing
A Tier 1 with ₹120 crore quarterly billing to Maruti Suzuki:
- Gross billing: ₹120 crore
- OEM auto-debit aggregate: ₹9.6 crore (8% short-pay)
- Reason-coded debits raised: ₹3 crore
- FOMP back-charges: ₹1.8 crore against 47 warranty claim IDs
- JIT shortage debits: ₹52 lakh on 23 line-side shortage events
- Quality penalty deductions: ₹38 lakh on PPM excess and line rejection
- Line-stop charges: ₹14 lakh (8.5 line-stop hours at ₹1.65 lakh/hour)
- Tooling adjustment credits: ₹12 lakh on three over-cap programmes
- Technical service deductions: ₹4 lakh on engineer visit days
- Net Maruti receipt for the quarter: ₹110.4 crore
- GST credit notes to be issued by 30 November (Section 34 cutoff): on ₹2.4 crore of accepted debits = ₹67 lakh GST reversal
- Rule 37 ageing buckets: ₹78 lakh sitting in 90-day bucket, ₹22 lakh in 150-day bucket — action triggered
- Section 393(1)(a) code 1002 deducted on subcontract pass-through: ₹14 lakh quarterly challan
Without a reason-coded settlement view, the quarter closes 11-14 days late and at least 30% of the debit base goes unrecovered from Tier 2 sub-suppliers.
ACMA standardisation reference
The Automotive Component Manufacturers Association of India (ACMA) publishes commercial-term templates and supplier-rating frameworks aligned to OEM auto-debit regimes. Tier 1 reconciliation systems typically encode ACMA’s standardised debit taxonomies and OTIF (on-time-in-full) score weights into the vendor master.
What automated reconciliation changes
Manual OEM settlement reconciliation at a multi-OEM Tier 1 is a 10-14 day month-end exercise with material recovery leakage from Tier 2 pass-throughs. Purpose-built reconciliation software India treats each debit reason code as a structured variance stream and surfaces only the lines that fail to match. TransactIG carries 24+ industry presets including a configuration that handles OEM auto-debits, FOMP running accounts, GST credit-note timing under Section 34, Rule 37 ageing, and the Section 393(1)(a) deduction map. Customer outcomes include match-rate improvement from 51% to 88% and exception rates moving into the sub-15% band post-implementation. Build is two-to-four weeks on AWS Mumbai (ISO 27001:2022). For the inbound procurement equivalent see three-way matching software India. For the full TDS code reference see TDS payment codes 1001-1092 India.