Two categories, one truck
A surprising number of Scope 3 inventories get Categories 4 and 9 wrong, and it's rarely because the underlying freight data is missing. It's because teams assume the boundary between the two categories is directional — inbound goods go in Category 4, outbound goods go in Category 9 — when the GHG Protocol actually draws the line somewhere else: who pays for the transportation.
Getting this wrong doesn't just mislabel emissions. It causes two very specific failure modes: double-counting the same shipment in both categories, or dropping it entirely because each team assumed the other was covering it.
What Category 4 actually covers
Category 4, Upstream Transportation and Distribution, captures emissions from moving purchased goods from your suppliers to your own operations, using vehicles and facilities you don't own or operate. That part matches most people's intuition: freight bringing raw materials or components to your factory or warehouse sits here.
But Category 4 also includes something less intuitive — transportation and distribution services that your company pays for, even when the goods are already sold and heading to a customer. If your company contracts and pays the logistics provider to move finished product out to distributors or retailers, that outbound leg is still an upstream category item, because you are the one purchasing the transportation service. The category is defined by the purchasing relationship for the transport, not by whether the goods are inbound or outbound.
What Category 9 actually covers
Category 9, Downstream Transportation and Distribution, covers transportation and distribution of sold products occurring after the point of sale, in vehicles and facilities not owned or controlled by the reporting company, where someone other than the reporting company pays for it. This typically includes retailer-operated distribution, third-party logistics arranged and paid for by a customer or distributor, and storage at downstream facilities.
So the practical test isn't "is this before or after we sold the product," it's "who holds the contract and pays the invoice for this leg of transportation." A shipment from your distribution center to a retailer's warehouse is Category 4 if you pay the carrier. The exact same physical movement is Category 9 if the retailer arranges and pays for the pickup.
Where the double-counting happens
The most common error is organizational, not conceptual. Logistics, sales, and sustainability teams often work from different assumptions about which category the inventory is tracking, and nobody reconciles them.
A few patterns show up repeatedly:
- A company reports all outbound freight under Category 9 by default, because "outbound equals downstream" feels intuitive, even though the company itself paid the freight bill — meaning it should sit in Category 4, and reporting it under 9 while a separate spend-based estimate also picks up freight spend under Category 4 results in the same tonnage counted twice.
- A company that sells through distributors assumes the distributor's transportation is automatically out of scope because it's "downstream and not ours." If the reporting company doesn't pay for that leg, it does belong in Category 9 — omitting it understates the inventory rather than correctly excluding it.
- Shared logistics networks, where a single truck carries both inbound components and outbound finished goods on different legs of a route, get allocated inconsistently between categories because nobody segments the trip by payer.
The fix is procedural: before assigning any transportation emissions line item to a category, ask who contracted and paid for that specific leg, not what the product's status was at the time. Build that question into the data collection template itself, so whoever is pulling freight invoices or carrier data is prompted to record the payer alongside the distance, mode, and weight.
Data quality still matters here
Once the boundary question is settled, the usual Scope 3 data quality hierarchy applies — spend-based estimates using freight cost and an emission factor sit at the weak end, average-data approaches using distance, weight, and mode-specific factors are a step up, hybrid methods combine the two, and supplier- or carrier-specific primary data (actual fuel consumption or carrier-reported emissions per shipment) is the strongest. Many companies start Category 4 and 9 estimates with spend-based methods because freight invoices are easy to pull, then migrate toward distance-and-mode average data as logistics teams get involved and can supply shipment-level detail. The category boundary and the data quality level are separate problems — fix the boundary first, or you'll just get a more precise version of the wrong number.
Why this matters beyond the inventory
For companies facing supply chain disclosure obligations — whether under CSRD, California's SB 253, or BRSR in India — transportation categories are often among the first line items auditors or assurance providers probe, precisely because the upstream/downstream split is a known source of error. A clean, documented payer-based allocation methodology, applied consistently across reporting periods, is one of the simpler things to get right in a Scope 3 inventory, and one of the more commonly audited.
If your logistics data is scattered across carrier contracts, ERP freight codes, and distributor agreements, that's a measurement and data architecture problem before it's a reporting problem. Scope 3 Emissions works with companies on exactly this kind of category-level inventory build-out — reach out at carbon@digi.ai.in if Categories 4 and 9 are where your current inventory is weakest.