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Auto-component suppliers dispatching 8-15 ASNs in a week to the same OEM plant cannot raise 14 separate tax invoices — OEM billing cycles, e-invoice IRN administration and GSTR-1 line counts all force consolidation. But Section 31 of the CGST Act fixes the latest legal moment for invoice issue, and the 7-day non-continuous-supply window is the binding constraint. Suppliers that consolidate beyond the window without documented continuous-supply contractual basis face Section 122 penalties and GSTR-3B mistiming, and break ASN-to-invoice linkage for downstream Section 34 credit-note treatment.
Determine whether the contract legally constitutes continuous supply (rare for JIS) or non-continuous periodic supply (the norm). For non-continuous, set billing-window length within 7 days from first dispatch; issue one consolidated e-invoice (IRN) with document date equal to close of billing window, generated within 24 hours of that date. Maintain an ASN-to-invoice register linking each ASN reference to the consolidated invoice IRN. For Section 34 returned goods, raise credit notes against the consolidated invoice IRN, not the originating ASN. Match billing-cycle close to OEM billing cycle (Tata weekly, Maruti monthly under continuous-supply contract, Bosch fortnightly).
Per-OEM-plant billing-cycle master with cycle length, close-of-window day and continuous-supply contractual flag; ASN-to-invoice consolidation register keyed by consolidated invoice IRN; e-invoice generation routine with document-date locking to close-of-window date; Section 34 credit-note workflow with consolidated-invoice IRN reference; GSTR-1 line aggregation per consolidated invoice; OEM-side consolidation log for receivables reconciliation.
A per-OEM-plant periodic-invoicing pack with billing-window calendar, ASN-to-IRN consolidation register, Section 31 timing-of-supply audit trail, and reconciliation between supplier-issued consolidated invoices and OEM-side consolidation receipts. Downstream support for Section 34 credit-note linkage and GSTR-1 / GSTR-2B alignment at the OEM.
A Pune-based Tier-1 stamping supplier dispatches 14 ASNs to Tata Motors Pune across a single week — daily JIS supply against firm 862 call-offs covering six body-in-white panel part-numbers. The supplier’s first instinct is to raise 14 tax invoices. The OEM accounts-payable team will not process 14 invoices for a single weekly billing cycle; the e-invoice portal would tolerate it, but GSTR-1 line-count balloons and the OEM-side periodic reconciliation breaks. The correct construction — multi-ASN single invoice consolidation auto component — is one consolidated weekly tax invoice with an ASN-to-invoice register linking the 14 ASNs to the single IRN, raised within Section 31’s timing-of-supply window. The mechanics are not obvious.
Quick reference
| Concept | Mechanism | Typical window | Tax rule |
|---|---|---|---|
| Continuous supply | Contractually defined periodic supply | Monthly under explicit contract | Section 31(4) |
| Non-continuous supply | Default for JIS / JIT dispatch | 7 days from first dispatch | Section 31(1) |
| Tata Motors PV cycle | Weekly | Mon-Sun close, IRN Monday | Section 31(1) |
| Maruti Suzuki cross-plant | Monthly under continuous-supply framing | Month-end close | Section 31(4) |
| Bosch (non-JIS) | Fortnightly | Two-week close | Section 31(1) |
| Hyundai HMI | Weekly | Sun-Sat close | Section 31(1) |
| e-Invoice line limit | 1,000 lines per IRN | Per consolidated invoice | e-Invoice schema |
| Section 34 credit note | Reference consolidated IRN, not ASN | Within 30 Nov of next FY | Section 34 |
What does Section 31 require for invoice timing
Section 31(1) of the CGST Act states that for a supply of goods involving movement, the registered person supplying the goods shall issue a tax invoice before or at the time of removal of goods for supply to the recipient. Rule 47 of the CGST Rules supports the same construction. Read strictly, this would require one invoice per dispatch — which is operationally impossible at JIS-cycle volumes.
Two accommodations exist in practice:
- Continuous supply of goods under Section 31(4) — where the contract specifically defines the supply as continuous, the invoice may be issued before or at the time at which each successive statement of accounts is issued or each successive payment is received. This permits a longer billing cycle (typically monthly) but requires explicit contractual framing — a general purchase order is not enough.
- Periodic-billing convention for non-continuous supply — industry has settled on a maximum 7-day window from first dispatch in the billing cycle to invoice issue. This is not codified in statute, but is the longest gap consistently accepted by audit and the GSTN portal without challenge. Most Indian OEMs run weekly billing cycles structured exactly to fit this window.
For finance, the practical rule is: if the contract does not say “continuous supply” in those words, treat the supply as non-continuous and run a weekly cycle.
What are the OEM billing-cycle patterns
The major Indian OEM patterns:
- Tata Motors Passenger Vehicles (Pune, Sanand) — weekly billing cycle, Sunday-to-Saturday window, supplier raises consolidated invoice on Monday with document date as the prior Saturday. ASN references for all dispatches in the week are listed in the supplier’s ASN-to-invoice register and on the e-invoice line-item narration.
- Maruti Suzuki (Manesar, Gurgaon, Kharkhoda) — monthly consolidation for cross-plant supplies where the contract explicitly defines continuous supply. Supplier raises one consolidated invoice at month-end. Where the contract does not so define, a weekly cycle is used instead.
- Bosch (Bidadi, Naganathapura, Nashik) — fortnightly cycle for non-JIS supplies, weekly for high-volume sequenced supplies. Document date is close-of-cycle Saturday; IRN generation Monday.
- Hyundai Motor India (Chennai) — weekly, Sun-Sat close.
- Mahindra (Chakan, Nashik) — weekly for PV programmes, fortnightly for CV components.
- Ashok Leyland (Hosur, Ennore) — fortnightly for most programmes.
- Bajaj Auto (Chakan, Waluj) — weekly for sequenced supply, fortnightly otherwise.
Each pattern carries its own ASN-tagging convention. Tata uses the SAP scheduling-agreement number plus delivery-document number; Maruti e-Nagare uses a portal-generated dispatch reference; Bosch SupplyOn uses an ASN reference.
How does the e-Invoice IRN constrain consolidation
The e-invoice schema (NIC IRP) permits up to 1,000 line items per IRN. A consolidated weekly invoice covering 14 daily ASNs with 6 part-numbers each carries 84 lines — well within the limit. Most auto-component consolidation does not approach the line-count limit.
The binding constraint is the document date and IRN-generation date. Three rules:
- The e-invoice document date is the invoice date for tax purposes. Output GST liability accrues to this date.
- IRN generation should be within 24 hours of document date. Backdated IRN generation is accepted by the portal but is non-compliant under the e-invoice notification timing.
- If the document date is more than 7 days before IRN generation, output-liability mistiming and Section 122 invoicing penalties become a real exposure.
Best practice: close the billing window on Saturday, set document date Saturday, generate IRN on Monday morning. The 36-48 hour gap is within the universally accepted operational window.
How do you reconcile individual ASN line-items back to one consolidated invoice
The supplier maintains a structured ASN-to-invoice register. Per consolidated invoice IRN, the register holds:
| Field | Source |
|---|---|
| Consolidated invoice IRN | e-Invoice portal |
| Invoice document date | Close of billing window |
| ASN reference | Supplier dispatch system |
| Dispatch date | ASN |
| OEM plant code | ASN ship-to |
| Part number | ASN line |
| Quantity | ASN line |
| Unit value | Scheduling-agreement price |
| Line value | Computed |
| GSTIN-place-of-supply | OEM plant master |
The OEM does similar matching at its end. Two recurring reconciliation breaks:
- Window-boundary drift — an ASN dispatched late on the Saturday close gets logged the next day and rolls into the next-window invoice. The current week’s invoice is short by the value of those parts; the next week’s invoice carries an extra ASN. OEM books show the GRN in the current week but the invoice in the next week, creating an unmatched GRN-without-invoice for one week.
- Section 34 credit-note linkage — when defective parts dispatched in a specific ASN are returned and a Section 34 credit note is required, the credit note must reference the consolidated invoice IRN, not the originating ASN. Many supplier ERPs default to the ASN reference; this breaks the GSTN credit-note linkage and causes ITC reversal complications at the OEM. The supplier’s ASN-to-invoice register is the lookup that fixes the credit-note IRN reference.
For the broader EDI-ASN-GRN-invoice chain see EDI 830, 862, 856 for Indian auto-component suppliers and the cluster sub-pillar automotive component manufacturing reconciliation in India.
Three-Way Match Exception Cost Calculator
Quantify the cost of unresolved ASN-to-invoice consolidation breaks — window-boundary drift, missing IRN-ASN linkage and broken Section 34 credit-note references age into accepted losses if not closed in cycle.
Open the Exception Cost Calculator →Worked example — Pune Tier-1, 14 ASNs to Tata Motors Pune
A Pune-based stamping Tier-1 supplies six body-in-white panel part-numbers to Tata Motors Pune on daily JIS schedule. Week of 8-14 June 2026:
- 14 ASNs dispatched across the week — 2 per day for most days, 3 on Wednesday
- Six part-numbers: front fender LH/RH, rear quarter LH/RH, hood inner reinforcement, dash panel
- Total dispatched quantity: 4,820 units across all part-numbers
- Total line value: ₹61.4 lakh at scheduling-agreement prices
- IGST (inter-state Maharashtra to Maharashtra is CGST + SGST): ₹11.05 lakh
- Total invoice value: ₹72.45 lakh
Invoice construction:
- Billing window: Sunday 8 June to Saturday 14 June
- Consolidated invoice document date: 14 June 2026 (Saturday)
- IRN generation: 16 June 2026 (Monday morning, within 48 hours of document date)
- Invoice line-items: 6 part-numbers consolidated to single lines per part with summed quantity, or 14 lines per ASN if OEM prefers ASN-level visibility — Tata convention is part-level consolidation with ASN references in narration
- ASN-to-invoice register: 14 ASN references logged against the consolidated IRN
- GSTR-1 reporting: single B2B line for the consolidated invoice, in the June 2026 return
Reconciliation outcome:
- Tata GRN-side consolidation: 14 GRNs logged across the week, matched to one supplier invoice in periodic reconciliation
- Output GST liability: ₹11.05 lakh accrued to 14 June, paid in 20 July GSTR-3B
- ITC at Tata: claimed in GSTR-2B against the consolidated IRN for June 2026
What does the Section 393 / Section 393(1)(k) overlay look like
Section 393(1)(k) (legacy 194Q) requires the OEM (buyer) to deduct TDS at 0.1 percent on the consolidated invoice value (or aggregate supplier-purchase value crossing ₹50 lakh in the FY). Two interactions:
- The 393(1)(k) deduction is on the gross invoice value of the consolidated weekly invoice — not on each ASN
- The supplier’s Form 26AS shows one TDS credit per OEM remittance — not one per ASN
- Reconciliation of 393(1)(k) credit to consolidated-invoice issued is straightforward but breaks if the OEM mistakes a single ASN value for the invoice value
For the broader payment-code reference see TDS payment codes 1001-1092 India and Section 393 TDS new Income Tax Act reconciliation.
ACMA authority reference
For OEM-supplier billing-cycle standardisation, ASN-to-invoice consolidation practice and periodic-invoicing conventions across the Indian Tier-1 supply base see the Automotive Component Manufacturers Association of India (ACMA).
What automated reconciliation changes
Maintaining a defensible ASN-to-invoice register across 4-8 OEM plants, 80-200 part-numbers and weekly cycles is a continuous accounts-receivable team exercise. Purpose-built auto component reconciliation software India holds the per-OEM-plant billing-cycle master, the Section 31 timing window, the e-invoice IRN-generation calendar and the ASN-to-IRN consolidation register in one frame. Customer outcomes include match rate improvement from 51 percent to 88 percent on revenue-grade ledgers. Build is two-to-four weeks on AWS Mumbai (ISO 27001:2022). For the inbound procurement match see three-way matching software India.