When the same product enters your stock at three different prices across a month, which of those prices do you use when it finally sells? That is the problem inventory valuation solves, and the two methods most Indian sellers, distributors and manufacturers choose between are FIFO (First-In, First-Out) and the weighted average cost method. The choice is not just an accounting formality — it changes your reported cost of goods sold (COGS), your gross margin, and the value of closing stock on your balance sheet.
This article walks through both methods with a worked example using the same purchase and sale data, compares them side by side, and explains where the choice actually matters for a GST-registered business.
What Inventory Valuation Decides
Every time you buy stock, you record a quantity and a cost. Every time you sell, you need to answer two questions: how much did those units cost you (COGS), and what is the remaining stock worth (closing inventory value). If purchase prices never changed, this would be trivial. In practice, raw material costs, supplier rates and freight mean the same SKU is bought at different unit costs across the year. Inventory valuation is the rule you apply consistently to split the total purchase cost between "sold" and "still in stock."
This matters for three practical reasons: it determines your reported profit for a period, it affects the inventory figure you would show a lender or investor, and it should stay consistent period to period so your numbers are comparable — switching methods opportunistically is not good practice and can invite scrutiny.
FIFO (First-In, First-Out) Explained
How FIFO Works
FIFO assumes the oldest stock in your warehouse is sold first, regardless of what physically leaves the shelf. When you record a sale, the costing works backward through your purchase batches in the order they were received, "using up" the earliest batches first until the sold quantity is fully accounted for. FIFO tends to mirror how many businesses actually manage physical stock — especially goods with a shelf life — which is one reason it is widely used.
Worked Example: FIFO in Practice
Take a SKU — TSH-BLU-M, a cotton T-shirt — with the following purchase history in a month:
| Date | Quantity | Rate | Value |
|---|---|---|---|
| 5 Jan | 100 | ₹200 | ₹20,000 |
| 15 Jan | 150 | ₹220 | ₹33,000 |
| 25 Jan | 100 | ₹240 | ₹24,000 |
| Total | 350 | — | ₹77,000 |
On 28 Jan, you sell 220 units. Under FIFO, you consume the 5 Jan batch first (100 units at ₹200 = ₹20,000), then move to the 15 Jan batch for the remaining 120 units (120 × ₹220 = ₹26,400).
COGS for this sale = ₹20,000 + ₹26,400 = ₹46,400. Closing stock is 130 units: 30 units left from the 15 Jan batch (30 × ₹220 = ₹6,600) plus the full 25 Jan batch (100 × ₹240 = ₹24,000), a total of ₹30,600.
Weighted Average Cost Method Explained
How Weighted Average Works
The weighted average method does not track individual batches at all. Instead, every time stock is purchased, you recalculate a single blended cost per unit for the entire quantity on hand, and every sale — regardless of when the stock was bought — is costed at that current average rate.
Worked Example: Weighted Average in Practice
Using the same purchase data, total cost across all three batches is ₹77,000 for 350 units, giving a weighted average cost of ₹220 per unit (₹77,000 ÷ 350).
For the same sale of 220 units on 28 Jan: COGS = 220 × ₹220 = ₹48,400. Closing stock is 130 units × ₹220 = ₹28,600.
Note that both methods must reconcile to the same total: ₹46,400 + ₹30,600 = ₹77,000 under FIFO, and ₹48,400 + ₹28,600 = ₹77,000 under weighted average — only the split between "sold" and "in stock" differs.
FIFO vs Weighted Average: Side-by-Side Comparison
| Factor | FIFO | Weighted Average |
|---|---|---|
| Costing logic | Oldest purchase cost used first | Single blended average cost per unit |
| COGS in this example (220 units sold) | ₹46,400 | ₹48,400 |
| Closing stock value (130 units) | ₹30,600 | ₹28,600 |
| In a rising-price period | Lower COGS, higher reported profit | COGS sits between old and new prices |
| In a falling-price period | Higher COGS, lower reported profit | Smooths out price swings |
| Tracking complexity | Needs batch-level tracking | Simpler — one rate per SKU at a time |
| Typical use case | Perishables, batch/lot-tracked goods, fashion | Bulk commodities, fungible high-velocity SKUs |
Impact on Margins, GST Reporting and Decision-Making
Valuation method does not change your GST liability directly — GST is charged on the sale value of the invoice, not on your internal cost. But it does affect two things sellers care about: reported gross margin, which drives pricing decisions, and the inventory value used in your books alongside the HSN-wise summary you may reconcile against stock records. If your rates fluctuate a lot — a fashion SKU restocked every festival season, or an item priced against a volatile input — the method you choose can visibly shift month-to-month profit even though nothing changed operationally.
It also matters when comparing margin across SKUs or warehouses: mixing methods without a documented reason makes those comparisons unreliable.
Which Method Should You Choose
There is no single correct answer — it depends on the nature of your stock:
- If you hold perishable, expiry-dated, or batch/lot-numbered goods (pharma, food, cosmetics), FIFO usually matches physical reality and is easier to justify to an auditor.
- If you deal in high-velocity, fungible SKUs where individual batches do not matter to the customer (hardware, basic apparel, commodity accessories), weighted average is often simpler to maintain across a large catalog.
- If your supplier prices are broadly stable, the two methods will produce very similar numbers, and the choice matters less.
- Whichever you pick, apply it consistently across a financial year and document the change if you ever switch, since a valuation change affects comparability of your reported numbers period over period.
This is general accounting guidance, not personalised tax advice — if the choice materially affects your reported profit, it is worth confirming your approach with your CA.
How OneBooks GST Plans to Support Inventory Valuation
Inventory — including an item master, SKU-level stock ledger, HSN/SAC mapping, multiple warehouses, and valuation methods like FIFO and weighted average — is on the OneBooks GST roadmap, alongside the GSTR-1 automation and accounting software already available today. The intent is that once stock movements are recorded, valuation and the resulting COGS should flow through to your books without a separate manual reconciliation step. You can track how this is shaping up on the inventory software page.
If you are managing this manually today alongside marketplace sales, our related guides on managing multi-warehouse stock and on HSN/SAC codes for inventory cover the adjoining pieces of the same problem.
Frequently asked questions
Can I use different valuation methods for different products?
Yes, in principle you can apply FIFO to some SKUs and weighted average to others if there is a genuine operational reason — for example batch-tracked pharma stock versus bulk hardware. What you should avoid is switching a given SKU's method back and forth without documentation, since that undermines comparability of your reported numbers.
Does GST require a specific inventory valuation method?
GST is levied on the transaction value of a supply as per the invoice, not on your internal costing method, so there is no GST-specific mandate on FIFO versus weighted average. Your valuation method affects your books, P&L and closing stock value under standard accounting practice, not your GST liability directly.
Which method is easier to maintain without inventory software?
Weighted average is generally easier to maintain manually because you only need one current rate per SKU. FIFO requires tracking each purchase batch separately and knowing which batch a sale draws from, which gets difficult at volume without a system that maintains a batch-wise stock ledger.
Does the valuation method affect the price I charge customers?
Not directly — your selling price is a business decision independent of costing method. However, since valuation affects your reported margin, it can influence how you interpret whether a price point is profitable, especially when input costs are volatile.
Can I switch from FIFO to weighted average later?
You can, but a change in valuation method is an accounting policy change and should be applied consistently going forward, and ideally discussed with your accountant since it affects the comparability of prior and future period results.
Using OneBooks GST for this workflow
For teams running this every return period, OneBooks GST handles GST invoicing and marketplace imports today; item master, stock ledger and warehouse workflows are on its roadmap.
OneBooks GST keeps source data, reviewed output and exports as separate records, so a figure can be traced back rather than reconstructed.
