Inventory Planning for a Fourth Quarter That Won't Behave Like Last Year's
Your Q4 inventory model has a long memory. It remembers last year's delivery times, the duty rates that applied, the promotion calendar, and the mix of prices and units that came with them. Then it hands all of that back to you as next quarter's plan.
That works when the year repeats itself. This one isn't repeating. Demand, duties, and delivery times have all moved, and each one changes a different number in your model. The better question to ask before the next purchase order goes out is which of last year's assumptions still hold, and who has checked.
Why Last Year's Pattern Is Now a Liability
A seasonal curve is a record. It shows what customers bought under one set of prices, one set of duty rules, and one set of delivery times. Change any of those inputs and the curve stops being a forecast. It becomes history with a new date on it. Inventory planning that treats the curve as a plan inherits every one of those conditions without checking them.
None of these shifts announces itself. A reorder point doesn't flag that the lead time feeding it is a year old. The model keeps producing confident numbers, and the confidence is the problem. Pushing more volume through an unexamined plan doesn't remove the constraint. It moves it, and in a holiday quarter it often lands on cash.
Read the Demand Signal in Units and Not in Dollars
The headline forecast is encouraging. The National Retail Federation expects US retail sales in November and December to grow 4.2% to $1.013 trillion, after 3.1% growth last year, and Mark Mathews, its chief economist, described consumers as "the bright spot in the economy," in NRF Forecasts 2026 Holiday Sales Growth as Consumers Remain Resilient.
A dollar forecast isn't a unit forecast. Bain & Company projects 4.5% growth in US holiday sales and says inflation is a major contributor to that nominal figure. It puts headline inflation at 3.4% and inflation excluding gas and energy at 2.5% in its 2026 Holiday Shopping Outlook. As a rough test, take 2.5% of price out of 4.5% in dollars and unit growth lands near 2% on average.
Averages hide the spread. The same 2026 Holiday Shopping Outlook places forecast growth for department stores, furniture and home furnishings, electronics and appliances, and food and beverage below 1%, while non-store sales grow 9% against 2.5% in stores. That split matters as much as the total, because a unit sold online ships from a different place than a unit sold on a shelf. Bain's own caution applies to every number in this paragraph, since "macroeconomic uncertainty could still tip the holiday season in either direction."
Dollar stock cover has already thinned in one part of the chain. The U.S. Census Bureau reports an August inventory-to-sales ratio of 1.18 for merchant wholesalers against 1.28 a year earlier, with sales up 15.6% and inventories up 6.4%, both before price adjustment, in its Monthly Wholesale Trade Report: August 2026. A ratio of dollars to dollars can't tell you how many units you hold. Count the units.
Grade the evidence behind each demand number as well. A confirmed order outranks a customer forecast, a forecast outranks last year's history, and history outranks an internal sales target. Plan each grade at its own confidence.
Reset Lead Times and Landed Cost Before You Reorder
Cost has moved as fast as demand. According to IEEPA Tariffs Struck Down, Replacement Tariffs Expired: What Importers Need to Know Now, an article in The Procurement Lawyer from the American Bar Association Section of Public Contract Law, the U.S. Supreme Court held on February 20 this year that the emergency statute behind earlier tariffs doesn't authorize them. A 10% global surcharge under a different law took effect February 24 and expired July 24. New duties of 10% or 12.5% on imports from 60 economies began that same day, and the article says pending investigations are expected to produce additional tariffs.
Those are American rules. Importers elsewhere face their own, and the point holds wherever duties can change faster than a purchase order cycle. The duty a product faces also depends on how it is classified and where it was made, according to the International Trade Administration guide Rules of Origin and Why They Matter, and on the entry date, as IEEPA Tariffs Struck Down, Replacement Tariffs Expired: What Importers Need to Know Now details. Landed cost belongs in the reorder decision as a live input. A cost that was right in July can be wrong by the time the next shipment arrives.
Delivery times need the same treatment. The Federal Reserve Bank of New York's Global Supply Chain Pressure Index rose to 1.28 in September from an upwardly revised 1.20 in August, Reuters reported in New York Fed says supply chain pressures rose last month relative to August. That sits below the May peak of 1.81 and far below the 4.43 reached in December 2021, but September nudged the index back up. August itself was revised upward after the first reading, so treat any single data point as provisional.
Check the lead-time field in your planning system. If it hasn't been refreshed from actual receipts in the past quarter, last year's delivery times are still setting this year's reorder points.
A reorder point rests on two numbers, expected demand during the lead time and the buffer for being wrong about it. Wider uncertainty on either one calls for a bigger buffer, and a bigger buffer costs money. Federal Reserve officials raised the US rate target in September and signaled another increase by year end, Reuters reported in New York Fed says supply chain pressures rose last month relative to August.
Toyota Motor Corporation builds its production system around making only what is needed, when it is needed, and in the amount needed, and it still stocks a minimum number of parts in advance, according to Toyota Production System. The company credits Taiichi Ohno with the basic framework of the method. The aim is a buffer sized to current conditions.
Set Trigger Points Before the Season Starts
Plans fail when a number moves and nobody has agreed about what it means. Decide in advance what you will do when a number crosses a line. Four lines cover most of the ground:
Landed cost. Set the unit cost at which you stop reordering, reprice, or switch to a substitute.
Sell-through. Compare weekly units with the forecast, and agree beforehand which gap triggers a reorder, a hold, or a markdown.
Slippage. Decide how many days of delay move an order to faster freight, and price that choice before you need it.
The last safe date. Name the day after which new orders can't land before the peak, and who owns stock that misses it.
Sort commitments by how easily you can reverse them. A custom order that can't be cancelled needs stronger evidence than stock you can redeploy to other customers.
I'd put a 13-week rolling review around these lines. That spans one quarter, and each week the team asks what changed in demand, cost, and delivery and which decisions can still wait. Test the plan against a lower, central, and higher demand case, and list which commitments become irreversible in each.
Watch the orders you receive, too. Hau L. Lee, V. Padmanabhan, and Seungjin Whang showed in Management Science that order variance may exceed sales variance and that the distortion tends to grow as you move upstream. Their paper, Information Distortion in a Supply Chain: The Bullwhip Effect, names four sources, price variations among them. A duty change is a price variation of a kind. If customers pulled orders forward ahead of one, those orders describe the tariff calendar and not consumption.
Make Inventory Planning a Standing Discipline
Most inventory planning gets approved once and defended afterward. A better habit treats the plan as a set of assumptions, each with an owner, a source, and a date when it expires. Units against price, channel mix, lead time, and landed cost make a workable starting list. Decision rights belong on the same list. Match approval authority to the money at risk, so routine reorders move quickly and large or hard-to-reverse commitments get a second look from every function involved.
I'd ask every leadership team one question before the holiday buy closes. Which assumption would we change first if it proved wrong, and what would tell us?
The figures here are American, and so are the duty rules. A business selling in another market faces different tariffs, a different peak calendar, and different shipping lanes. The discipline travels. The inputs must come from your own market, checked against your own receipts.
Last year's curve still has a use. It can't tell you whether its assumptions still apply, and that part of the work belongs to you.
When the Assumptions Behind Your Stock Plan Need a Second Look
Aspirations Consulting Group works with executives and other leaders at growth, transition, and performance-pressure moments, when demand, costs, and timelines shift faster than the plans built to handle them. ACG helps teams work through the operational, financial, and people questions that tend to arrive together, and decide where to act first. See how ACG works with leadership teams.
Keep Your Assumptions Current
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Thanks for reading!
~ Jerry Justice
Living to Serve, Serving to Lead™
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