Module 03: A single source of truth for ecommerce data
Fifteen apps, four numbers, no truth.
Every automation you build on top of disagreeing data will be confidently wrong.
Quick answer
A single source of truth in ecommerce means each type of data (stock, product details, orders, costs, policies) has one system that owns it, and every other system reads from it. For stock, the source of truth is the warehouse put-away count. Automate only after the systems agree, and stop automations when they do not.
Lesson 3 of 8 in our free AI automation guide. Read it in about 10 minutes, then work through the checklist at the end.
Why does data come before automation?
Automation repeats whatever it is fed. If Shopify thinks you have 40 units and the warehouse has 12, a stock sync that copies Shopify's number can oversell up to 28 units on every channel it touches, and an AI shopping assistant will recommend a product you cannot ship. Fixing the data is the cheapest automation project you will ever do.
Which system is the single source of truth for each kind of ecommerce data?
The one closest to the physical fact: the warehouse for stock, one catalog for product details, each channel for its own orders.
| Data | System of record | Rule |
|---|---|---|
| Sellable stock | Warehouse (3PL or WMS) put-away count; FBA and WFS for their own stock | Sync only put-away, never expected or received |
| Product details | One catalog (Shopify, a PIM or a master sheet) | Channels are edited from the catalog, not directly |
| Orders | Each channel creates; one hub collects | Count check daily: channel versus warehouse |
| Costs | Cost sheet or accounting | Dated; updated when fees or tariffs change |
| Policies | One written document | Website, marketplace settings and chatbot quote it |
What is the put-away rule?
Count stock only after the warehouse puts it away. Received is not the same as sellable: some units are damaged and some are not on a shelf yet. ShipBob's developer guide tells integrators: "Always use stowed_quantity when updating your system" (stowed means put away; developer.shipbob.com, checked Oct 20, 2026). Compare expected, received and put away on every inbound, and send each gap to a person.
How do you write data definitions?
Write one line each for the metrics you use: "available stock" (put away, minus reserved, minus buffer); "late order" (not shipped by the ship-by date); "contribution margin" (price minus every fee, ad cost, shipping and landed cost per unit). Use the same definition in every report and rule.
How do you find where your data disagrees today?
Take your top 10 SKUs and write down the stock count in every place it appears: each channel, the warehouse, FBA or WFS and any spreadsheet. Do the same for price and for the product title. Every row that does not match is a place an automation would go wrong. Fix those rows before you automate anything that reads them.
A first check often looks like this (illustrative · sample figures):
| SKU | Shopify | Amazon FBA | Walmart | 3PL put away | Spreadsheet | Finding |
|---|---|---|---|---|---|---|
| Bottle, 24 oz, black | 140 | 60 | 140 | 128 | 150 | Shopify and Walmart show 12 more than the shelf holds: gift-set sales are not reducing the single-bottle count |
| Bottle, 24 oz, white | 0 | 22 | 35 | 35 | 35 | Shopify shows zero after a failed sync; sales lost for two days |
| Lid, spare | 410 | 0 | 410 | 395 | 410 | The received count (410) was synced instead of put away (395); 15 units were damaged at receiving |
Three SKUs, three different causes. None of them needs AI to fix. Each needs an owner and a rule.
What happens when systems disagree?
The automation stops and asks a person. It never picks a number. Set a daily reconciliation: orders per channel versus orders at the warehouse; stock per channel versus put-away; payouts versus orders.
Key takeaways
- Each data type gets one owner system; others read.
- Stock truth is the put-away count.
- Definitions are written once and used everywhere.
- Disagreement stops the automation and alerts a person.
Do this now
- Fill in the five-row system-of-record table for your store.
- Compare stock for your top 10 SKUs across every channel and the warehouse today.
- Write your definitions of available stock, late order and contribution margin.
- Set one daily check: orders per channel versus orders received by the warehouse.
Tool for this lesson: your warehouse's inventory report and a reconciliation sheet; RELAY-03 Stock Flow and RELAY-01 Profit and Cash Pulse when you want it built.
Ecom Relays is not paid by and not affiliated with any tool listed. We name widely used tools so you know your options. Amazon, Walmart and Shopify are trademarks of their owners; Ecom Relays is not affiliated with them.
Most new stores take months to find steady sales, and some never do. Inventory, platform fees, freight and ad spend are paid by you. Automation saves time on repeat work. It does not create demand for a product.
A note on AI claims: the FTC has warned businesses not to exaggerate what their AI can do (FTC business guidance, "Keep your AI claims in check," Feb 27, 2023). We describe each tool from its own documentation, label vendor figures as vendor estimates and never say that AI will produce sales for you. AI here means software that drafts, sorts, checks and alerts. People still own the decisions.
The problem this lesson fixes
-
In owners' words:
"Our numbers live in spreadsheets nobody trusts."
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Cause:
data copied between systems by hand, with no owner for each type.
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Fix:
the system-of-record table and a daily reconciliation; when you want it built, Profit and Cash Pulse produces one owner dashboard from source data.
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Measure:
hours a week spent reconciling reports.
Talk it through with a real person
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Do I need an ERP for one source of truth?
No. You need a decision about which system owns each data type, written down and followed. An ERP helps at higher complexity, such as several warehouses, wholesale orders or complex purchasing, but many brands run well on their channels, a 3PL integration and a clear table like the one above.
What if FBA and my 3PL both hold stock?
Each owns its own stock. FBA's count is the truth for units in Amazon's warehouses, and the 3PL's put-away count is the truth for units it holds. Your order hub or inventory tool adds them up by where each pool is allowed to sell, so Shopify never offers units that sit in FBA unless you ship them that way.
How often should I reconcile?
Daily for orders and stock; monthly for payouts and 3PL invoices. The daily checks can be automated, with any mismatch sent to a named person. The monthly ones need a person to read them, because deciding what to dispute is a judgment call.
Why not sync received stock to sell faster?
Because damaged and unshelved units are not sellable, and the oversells that follow cost more than the speed. On Walmart, cancellations are scored against a standard of 2% or below (Walmart Marketplace Learn, updated Jul 28, 2026), so an oversell is an account problem as well as an unhappy customer.
What about bundles?
Divide each component's put-away stock by how many of that component one bundle uses; the smallest result is the number of bundles you can sell. A gift set with two bottles and one lid, with 40 bottles and 25 lids in stock, can sell 20 sets, not 25. Every sale of the set must reduce each component too.
Who owns the data rules?
The ops lead, with one named owner per data type. The owner decides the definition, checks the daily reconciliation and approves any change to how the data flows. Without a named owner, disagreements sit unresolved and automations quietly act on the wrong number.
Sources3 sources
- 01marketplacelearn.walmart.comchecked Oct 20, 2026Primary
- 02developer.shipbob.comchecked Oct 20, 2026Primary
- 03ftc.govchecked Oct 20, 2026Primary
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