Most Indian manufacturers and traders adopt an inventory costing method by accident—whatever their accounting software defaults to—then discover during a GST audit that the method they chose either inflates or compresses their input tax credit (ITC) recovery.
Under the GST Rules, 2017, your choice of valuation method (FIFO, LIFO, weighted average, or standard cost) directly determines: (1) the closing-stock value that feeds your next month's opening stock and cost of goods sold (COGS); (2) the quantity-weighted average purchase price used to value withdrawals for personal use or gifts; and (3) how GST officers challenge your ITC claim when input invoices are dated before a rate change or involve multiple suppliers at different prices. This article walks you through the mechanics of each method, the GST-specific traps, and how to lock in your choice so auditors cannot unpick it mid-year.
Market signals
Under FIFO (First In, First Out), you value closing stock at the most recent purchase cost, which means older (cheaper) purchases flow into COGS first. This depresses reported profit—attractive for tax minimisation—but creates a friction point under GST: when you claim ITC on old invoices at a lower tax rate and later purchase the same material after a GST rate hike (e.g., 5% → 12% on certain categories in April 2024), the GST officer sees the rate gap and may disallow the older ITC claim, arguing you should have matched newer inputs to cost-of-sale. To defend FIFO ITC claims, you must document that the older batch was physically sold first (store location maps, bin cards, batch-tracking logs per COGS). Without this trail, the officer defaults to treating all purchases as a homogeneous pool.
Weighted average (WAVG) pools all purchases by cost per unit, so if you buy 100 units at ₹100 and 200 units at ₹150 in the same month, your COGS uses a blended rate of ₹133.33 per unit. Under GST Rule 31, your ITC is based on the tax invoices you hold; WAVG does not change the ITC entitlement itself, but it does smooth the profit impact, making audits quicker because the officer sees no artificial profit swings from old-vs-new input prices. However, WAVG hides whether your suppliers are raising or cutting their input costs, so you may miss pricing-power opportunities with customers (if your RM costs fall 8%, your gross margin gains 8%, but WAVG masks the timing of the gain). WAVG is GST-compliant if your weighted-average calculation is done monthly and documented in a cost ledger or ERP; auditors rarely dispute it.
Standard cost sets a fixed per-unit cost for a period (e.g., ₹150 per widget for Q1 FY26), then records actual purchases at that standard; variances (unfavourable if actual ₹160 > standard ₹150, favourable if actual ₹140 < standard ₹150) are tracked separately and adjusted to COGS quarterly or annually. Under GST, your ITC claim must still match the actual tax invoices you received; you cannot claim ITC on a 'standard' purchase price that differs from what you paid. If you use standard cost for financial reporting but do not reconcile variances to actual invoices monthly, the GST officer will treat unreconciled variances as unsupported COGS and disallow corresponding ITC. Reconciliation requires
Frequently asked questions
Your choice of valuation method (FIFO, LIFO, weighted average, or standard cost) directly determines closing-stock value, COGS, and how GST officers challenge your ITC claims when input rates vary or change.
You must maintain store location maps, bin cards, and batch-tracking logs per COGS to prove older batches were physically sold first and justify ITC claims on older invoices at lower tax rates.
When GST rates increase after you claim ITC on cheaper older purchases, officers may disallow the older ITC claim, arguing you should match newer inputs to later cost-of-sales instead.