Walk into almost any warehouse, storeroom, or back office and you'll find it: a shelf of parts nobody has touched in eighteen months, a pallet of last season's colorway, a box of components for a product line you discontinued. Your books still say that inventory is worth what you paid for it. Your gut says otherwise.
That gap between what your accounting records claim and what the stuff is actually worth is one of the most common — and most commonly ignored — problems in small business bookkeeping. Left unaddressed, it inflates your assets, overstates your profit, and can trigger an unpleasant conversation with your accountant (or worse, a lender or investor) when the truth finally surfaces.
Here's how to recognize obsolete and slow-moving inventory, value it correctly, and record the write-down without making a mess of your books.
What "Obsolete" and "Slow-Moving" Actually Mean
These two terms get used interchangeably, but they describe different problems:
- Slow-moving inventory still sells — just much more slowly than you planned when you bought or built it. It's not dead, but it's tying up cash and shelf space longer than it should.
- Obsolete inventory has effectively stopped selling. The product was discontinued, the technology changed, the fashion season passed, or a component was superseded by a newer part number. It may never sell at a normal price again.
For most businesses that carry inventory, this isn't a rounding error. Industry estimates put slow-moving and obsolete ("SLOB") stock at roughly 20–25% of total inventory value across a typical company, and in fast-cycle categories like fashion, consumer electronics, and seasonal goods, the obsolescence rate alone can run 6–12% of inventory value in a given period. If you haven't looked at your aging inventory report recently, there's a good chance a meaningful chunk of your balance sheet is overstated right now.
How to spot it before it becomes a surprise
You don't need fancy software to catch this early — you need a routine. A few practical signals:
- Inventory age. Run an aging report and flag anything that hasn't moved in 6, 12, or 18 months (the right threshold depends on your industry — a bakery's "slow-moving" is a hardware store's "brand new").
- Turnover ratio by SKU, not just in aggregate. A healthy overall turnover number can hide a handful of dead SKUs dragging down an otherwise fine inventory position.
- Demand and style shifts. If a supplier discontinues a part, a competitor undercuts a product line, or customer preferences move on, treat that as a trigger to review the related stock — don't wait for the annual count.
- ABC/XYZ analysis. Classify inventory by value (A/B/C) and demand variability (X/Y/Z) so your review time goes to the SKUs that actually matter, not evenly across everything you stock.
Make this a monthly habit, not a year-end scramble. Comparing recent sales activity against on-hand quantities once a month — even with a simple spreadsheet — catches problems while you still have options (discount it, bundle it, return it to a vendor) instead of after it's truly worthless.
The Accounting Rule: Lower of Cost or Net Realizable Value
Under U.S. GAAP (ASC 330), inventory measured under FIFO or average cost must be reported at the lower of cost or net realizable value (NRV) — commonly abbreviated LCNRV. This replaced the older "lower of cost or market" rule for most companies in 2015, simplifying the comparison to just two numbers.
Net realizable value is defined as:
Estimated selling price in the ordinary course of business, minus reasonably predictable costs of completion, disposal, and transportation.
In plain terms: what could you actually sell this for, today, minus whatever it costs you to get it out the door?
The rule in one line: if NRV falls below your recorded cost, you write the inventory down to NRV and recognize the difference as a loss immediately. You never write inventory up above its original cost, even if NRV later recovers — the write-down establishes a new, lower cost basis, and reversals are prohibited under GAAP.
A simple example
Say you're carrying 80 units of a slow-moving component at a cost of $5,000 each — $400,000 total. The product line has been discontinued, and the best offer you can realistically get is $3,200/unit, with an estimated $200/unit in disposal and handling costs to liquidate it.
- Net realizable value per unit: $3,200 − $200 = $3,000
- Cost per unit: $5,000
- NRV is lower than cost, so you write down to NRV: ($5,000 − $3,000) × 80 units = $160,000 write-down
That $160,000 doesn't disappear — it hits your income statement as a loss (or flows through cost of goods sold, depending on your presentation), and your inventory asset on the balance sheet drops by the same amount. Painful, but accurate. The alternative — leaving it at $400,000 — just delays the pain and overstates your financial position in the meantime.
How to Record the Write-Down
There are two common approaches, and which one fits depends on the size and predictability of the problem.
1. Direct write-down. Debit a loss/expense account (e.g., "Loss on Inventory Write-Down" or directly to COGS), credit Inventory. Simple, and appropriate for a one-time, specific event — you know exactly which SKUs are impaired and by how much.
2. Allowance (reserve) method. Instead of reducing the inventory account directly, you debit an expense account and credit a contra-asset account — commonly called "Allowance for Obsolete Inventory" or "Inventory Reserve" — which nets against gross inventory on the balance sheet. This is the better approach if you're estimating obsolescence risk across a broad inventory pool (rather than identifying specific dead stock line by line), because it lets you build the reserve gradually based on aging trends and true up the estimate each period, similar to how a bad debt allowance works for receivables.
Either way, the core mechanics are the same: an expense goes up, and the inventory asset (net of any reserve) goes down. What you should never do is quietly reduce the inventory count without a matching entry, or bury the write-down inside an unrelated expense line where it can't be tracked or explained later.
The Tax Side: What the IRS Actually Allows
Financial-statement rules (GAAP) and tax rules don't automatically match, and inventory write-downs are a classic place where they diverge. The IRS's controlling regulation is Treasury Regulation §1.471-2(c), which addresses "subnormal goods" — inventory that's unsalable at normal prices because of damage, imperfections, shop wear, style changes, odd lots, or similar causes.
The key requirements for a write-down to hold up on your tax return:
- The goods must actually be offered for sale at the reduced price, in the ordinary course of business, within a period ending no later than 30 days after the inventory date. A write-down based purely on internal estimation — with no actual offer to sell — generally won't survive IRS scrutiny.
- You value the goods at their bona fide selling price, minus direct costs of disposition — not an arbitrary internal estimate of impairment.
- The burden of proof is on you, the taxpayer, to show the goods genuinely meet the "subnormal" classification and to document how they were offered and ultimately disposed of. Keep records: price lists, liquidation invoices, marketplace listings, whatever demonstrates the actual offer.
This is a narrower standard than the book (GAAP) NRV calculation, which can be based on estimates and forecasts. In practice, many small businesses record a full write-down for financial-statement purposes but can only deduct the portion that meets the tax code's stricter "actually offered for sale" test — creating a temporary book-tax difference that your accountant will need to track. If you're using book reserves to also support the tax deduction, talk to your CPA before assuming that estimate carries over; the IRS treats the two very differently.
Prevention Beats Cleanup
A write-down is a correction, not a strategy. The businesses that handle obsolete inventory well aren't the ones with the best write-down process — they're the ones that rarely need one, because they:
- Order in smaller, more frequent batches for anything with uncertain or seasonal demand
- Set automatic aging alerts (60/90/180 days) instead of relying on someone noticing
- Negotiate return or exchange rights with suppliers before committing to large orders
- Run clearance or bundle promotions on slow movers before they become fully obsolete — a discounted sale beats a write-off every time, because you at least recover some cash and avoid the loss entirely
Keep Your Inventory Numbers Honest, Automatically
Catching slow-moving stock early — and recording the write-down correctly when it happens — depends on being able to see your inventory and financial data clearly, without digging through disconnected spreadsheets or opaque software. Beancount.io provides plain-text accounting that gives you complete transparency and version-controlled history over every entry, including inventory adjustments and write-downs, so nothing gets buried in a black box. Get started for free and see why developers and finance professionals are switching to plain-text accounting.