RMPV Calculation Formula for Auto-Component Suppliers: Step-by-Step Worked Examples

The RMPV calculation looks simple on paper. In practice it is where margin recovery succeeds or fails. This is the operator-level companion to the RMPV clauses explainer — the step-by-step guide to actually computing the RMPV calculation formula auto component India claim, with three worked examples that cover the realistic complexity an auto-component finance team faces every quarter. We close with the quarter-end provisioning entry under Ind AS 37 and the true-up.

Quick reference

The base formula

For a single material on a single part:

Claim_rupees = (Current_Index − Base_Index) × Material_Weight_per_part × Quantity_Supplied × Adjustment_Factor

Where:

• Current_Index is the new published value of the reference index for the revision period, expressed in ₹ per kilogram (or in ₹ per MT divided by 1,000 for steel)
• Base_Index is the index level locked at programme award, in the same unit
• Material_Weight_per_part is in kilograms
• Quantity_Supplied is the number of units shipped against the agreement during the revision period
• Adjustment_Factor is 1.0 by default, modified for clause-specific cases (trigger band, cap, supplier-absorption percentage)

The output is in rupees. Positive means the supplier raises a supplementary (debit) invoice — taxable upward revision; the GST flows in the current period under Section 12/13 time-of-supply. Negative means the supplier issues a GST credit note under Section 34 of the CGST Act, reducing output liability — subject to the OEM reversing ITC and the credit note being issued within the Section 34 window (by 30 November of the following financial year, or the annual return filing, whichever is earlier).

For multi-material parts, run the formula per material and sum.

Worked example 1 — single-material steel part with JPC HR coil

A stamping supplier supplies a heat-shield bracket to Maruti at Manesar. Programme details:

• Material: HR steel coil
• Material_Weight: 1.4 kg per part
• Base_Index: JPC HR coil at award = ₹58,200/MT = ₹58.20/kg
• Reference index: JPC monthly published HR coil
• Averaging method: monthly average
• Q1 Current_Index: ₹61,800/MT = ₹61.80/kg (the simple average of three monthly published values: ₹60.5, ₹62.1, ₹62.8)
• Quantity_Supplied in Q1: 84,000 units
• Adjustment_Factor: 1.0 (no trigger band, no cap, no absorption)

Step-by-step:

1. Index differential = ₹61.80 − ₹58.20 = ₹3.60 per kg
2. Per-part claim = ₹3.60 × 1.4 = ₹5.04 per part
3. Total Q1 claim = ₹5.04 × 84,000 = ₹4,23,360
4. Direction: positive (upward revision) → supplementary invoice
5. GST: charged at the component’s applicable rate on ₹4,23,360
6. Time of supply: current period (the period in which the supplementary invoice is issued, typically mid-Q2 after JPC publishes)
7. Form 26AS / TDS: the material-portion RMPV is not subject to Section 393(1)(k) TDS — the OEM’s TDS deduction continues to apply only to the conversion portion of the next regular payment

The supplier raises the supplementary invoice through Maruti’s e-Nagare portal in mid-July, after the JPC bulletin for the Q1 period publishes. Settlement lands in mid-August per the contractual 30-day window.

Worked example 2 — multi-material steel + aluminium with one index rising and one falling

A forging supplier supplies a stamped-and-welded bracket to Tata Motors. The part has two materials:

• Material 1: HR steel. 2.8 kg per part. Base_Index: JPC HR coil ₹61,400/MT = ₹61.40/kg. Averaging method: three-month moving average. Q1 Current_Index: ₹65,100/MT = ₹65.10/kg (a 6% rise).
• Material 2: Aluminium ingot (for a welded insert). 0.6 kg per part. Base_Index: LME aluminium $2,180/MT × INR 83.40 = ₹181,812/MT, plus 5% landing premium = ₹190,903/MT = ₹190.90/kg. Averaging method: monthly average LME. Q1 Current_Index: LME monthly average $2,090/MT × INR 83.50 = ₹174,515/MT plus 5% premium = ₹183,241/MT = ₹183.24/kg (a 4% fall).
• Conversion portion: ₹118/part, held fixed (not part of RMPV).
• Base price at programme award: ₹620/part.
• Quantity supplied Q1: 48,000 units.
• Adjustment_Factor: 1.0 for both materials.

Step-by-step per material:

Steel:

1. Index differential = ₹65.10 − ₹61.40 = ₹3.70 per kg
2. Per-part claim = ₹3.70 × 2.8 = ₹10.36 per part
3. Total Q1 steel claim = ₹10.36 × 48,000 = ₹4,97,280
4. Direction: positive → supplementary invoice for ₹4,97,280 + GST

Aluminium:

1. Index differential = ₹183.24 − ₹190.90 = −₹7.66 per kg
2. Per-part claim = −₹7.66 × 0.6 = −₹4.60 per part
3. Total Q1 aluminium claim = −₹4.60 × 48,000 = −₹2,20,800
4. Direction: negative → Section 34 credit note for ₹2,20,800

The supplier issues two separate documents because the GST events are opposite-direction:

• Steel supplementary invoice (₹4,97,280 + GST) — current-period GSTR-1 output
• Aluminium Section 34 credit note (₹2,20,800) — reduces output GST liability, subject to OEM reversing the corresponding ITC, and must be issued before the Section 34 cutoff (30 November of the following financial year)

The net position is +₹2,76,480 in the supplier’s favour. The two documents post separately in the supplier’s GST returns; they do not net to one document.

Negotiation reality. Tata’s purchase team disputes the steel averaging method, claiming the contract specifies monthly average and the supplier has applied three-month moving. The supplier and Tata reconcile contract language. Resolution in mid-Q3; the supplementary invoice is accepted at the originally claimed amount. The aluminium credit note is uncontested and posts in Q2 within the cutoff. Until acceptance, the supplier carries the steel claim as an Ind AS 37 provision against an OEM-dispute reserve.

Worked example 3 — non-linear escalation with a 3% supplier-absorption trigger band

A polymer-injection-moulding supplier supplies an interior trim component to M&M. Programme details:

• Material: PP-ABS blend
• Material_Weight: 0.95 kg per part
• Base_Index: Polymer benchmark ₹148/kg at award
• Reference index: named polymer grade bulletin
• Averaging method: monthly average
• Q1 Current_Index: ₹157.40/kg (a 6.35% rise)
• Quantity_Supplied in Q1: 1,20,000 units
• Trigger band: supplier absorbs the first 3% of index movement before claim kicks in

Step-by-step:

1. Raw index movement = (157.40 − 148) / 148 = 6.35%
2. Net of trigger band = 6.35% − 3.00% = 3.35% claimable
3. Effective Current_Index for claim = 148 × (1 + 0.0335) = ₹152.96/kg
4. Effective differential = ₹152.96 − ₹148 = ₹4.96 per kg
5. Per-part claim = ₹4.96 × 0.95 = ₹4.71 per part
6. Total Q1 claim = ₹4.71 × 1,20,000 = ₹5,65,200
7. Direction: positive → supplementary invoice

Equivalent formula form:

Claim = max(0, (Current_Index − Base_Index) − Trigger_% × Base_Index)
        × Material_Weight × Quantity × Adjustment_Factor

If the index movement had been only 2.5% (below the 3% trigger), no claim would be admissible. If the index had fallen, the trigger band typically symmetric — the OEM absorbs the first 3% of downward movement too, meaning the supplier issues a credit note only on the fall beyond 3%. The contract language must be checked: some agreements specify an asymmetric trigger (supplier absorbs upward, OEM absorbs downward) which is heavily supplier-unfavourable.

Handling the averaging method

The averaging method changes only the value of Current_Index, not the formula. Three common methods:

Monthly average. Sum the daily or weekly published index values across the calendar month; divide by the count. JPC publishes monthly already, so for steel this is straightforward — take the JPC monthly bulletin value. For LME, take the LME monthly average settlement (typically the official daily-close average for the month).

Three-month moving average. Take the arithmetic mean of the three most recent monthly averages. For a Q1 (ending June) revision under a three-month moving method, average April, May, June monthly averages.

Quarter-end spot. Take only the published index value at the close of the revision period. Volatile and only suits agreements where the OEM and supplier accept the single-point exposure.

The contract names the method. The most expensive disputes come from applying the wrong one.

Handling the publication and settlement lag

The reference index is only known after the revision period closes:

• JPC HR/CR coil bulletin publishes around 15 days after month-end. For a Q1 ending 30 June, the June JPC bulletin lands around 15 July; the three-month moving average for Q1 can only be finalised at that point.
• LME monthly average is finalised on the first business day of the following month. Q1 LME settlements are confirmed in early July.
• Polymer benchmark publication varies — typically mid-month after period close.

After publication, the contractual settlement lag adds another window — commonly 30 days. So a Q1 claim is computed in mid-July, the supplementary invoice or credit note is issued by end-July, and the cash settles mid-August.

Quarter-end provision under Ind AS 37. Because the supplier cannot wait for publication to recognise the position, an estimate is booked at quarter-end. The provision is computed against observed index movement up to the period close (using daily index data) and recognised as an income (for upward) or a liability (for downward) under Ind AS 37 — a present obligation arising from a past event (the goods supplied at base price) where the amount is reliably estimable. On publication, the actual claim is computed and a true-up entry posts the difference.

Quarter-end provision and true-up entry

For the steel claim in worked example 1 (₹4,23,360 expected):

Quarter-end provision entry (30 June):

Dr  RMPV Receivable (accrued income)        ₹4,23,360
    Cr  RMPV Income — to be billed                ₹4,23,360

(Provision recognised under Ind AS 37; this is income recognition before the supplementary invoice is issued, treated as a contract-modification revenue under Ind AS 115.)

On index publication and supplementary invoice issue (mid-July):

Assume the actual JPC monthly average comes in slightly higher than the daily-observed estimate — true-up of ₹15,000 favourable.

Dr  RMPV Receivable                          ₹15,000
    Cr  RMPV Income (true-up)                     ₹15,000

Dr  Trade Receivables (Maruti)               ₹4,38,360 + GST
    Cr  RMPV Receivable                            ₹4,38,360
    Cr  Output GST (current period)                 [at component rate]

On OEM acceptance and settlement (mid-August):

Dr  Bank                                     ₹4,38,360 + GST
    Cr  Trade Receivables (Maruti)                ₹4,38,360 + GST

For a downward claim, the provision is on the liability side and the credit note triggers the GST reduction within the Section 34 cutoff.

GST classification — Income Tax Act 2025 leaves GST untouched

The Income Tax Act 2025 changes the TDS framework (Section 393/394/413, payment codes 1001–1092). It does not change GST. RMPV GST treatment continues under the CGST Act:

• Upward revision: supplementary (debit) invoice. GST on the differential at the component’s rate. Output liability in the current period (Section 12/13 time-of-supply).
• Downward revision: credit note under Section 34. Reduces output liability subject to the OEM reversing ITC. Must be issued by 30 November of the following financial year, or the annual return filing, whichever is earlier. A credit note issued after the cutoff has no GST effect even if the operational price concession is conceded.

The OEM’s TDS deduction on the next regular payment applies Section 393(1)(k) at 2% (payment code 1012) on the conversion portion of the invoice — see the TDS payment codes 1001–1092 reference and the Section 393 master guide. The material-portion RMPV claim is not subject to TDS — it is a revision to a goods supply, not a payment for services.

Cross-cluster context

This formula guide is the operator-level companion to the RMPV clauses explainer and feeds the broader raw material price escalation clause reconciliation guide. It sits inside the automotive component manufacturing reconciliation sub-pillar and the manufacturing reconciliation pillar. For the JPC steel index reference, see JPC published Indian steel prices. This article will eventually anchor the RMPV Calculator interactive tool that ships in Wave B of the automotive-components content sequence.

What automated reconciliation changes

A spreadsheet-driven RMPV process loses on every dispute because the audit trail is brittle. Purpose-built reconciliation software India carries the per-material RMPV clause structure in the part master, ingests the index feed per period, applies the contractual averaging method, computes the per-part claim, splits upward and downward results into the right GST documents (supplementary invoice vs Section 34 credit note), watches the 30 November cutoff, books the Ind AS 37 provision at quarter-end, and trues up on index publication and OEM acceptance — with the full input-to-output worksheet preserved per claim for OEM-dispute defence. TransactIG ships 24+ industry presets including the auto-component RMPV preset. Customer outcomes include match-rate improvement from 51% to 88%. Build is two-to-four weeks on AWS Mumbai (ISO 27001:2022). For the Tier-2 procurement equivalent, see three-way matching software India.