Vendor Central (1P) vs Seller Central (3P): how stock planning differs
By Nitesh Sharma · 15/10/2026 · 7 min read
On Seller (3P) you decide when to send stock. On Vendor (1P) Amazon sends you purchase orders and you decide how much of each you can fill. Because the trigger, the lead time and the meaning of the word stock differ, a single sheet for both brings wrong numbers on one side or the other.
Who owns the stock
In Seller, the stock is yours until a customer buys it. You pay for the goods, the freight and the storage, and you send in more when you choose.
In Vendor, you sell to Amazon. Once Amazon receives the goods they are Amazon's stock. You do not push stock; Amazon pulls it by raising purchase orders (POs).
What starts a reorder
In Seller, your own plan starts the reorder: sales speed, stock and lead time lead to a date and a quantity (see the guide on reorder quantity).
In Vendor, the PO starts it. Amazon raises a PO for a quantity and a delivery window. Your job is to see POs early, check you can supply, and confirm what you can fill. Your own forecast matters, but it is for being ready, not for deciding what to send.
Fill rate: the number Vendor teams live by
Fill rate is the share of a PO you actually deliver. If a PO asks for 500 units and you deliver 400, fill rate is 80%. A low fill rate means lost sales on the shelf and a weaker standing with the buying team.
So Vendor planning starts with a question Seller planning does not have: of everything Amazon is asking for, how much can we really make or hold in time? A PO you cannot fill should be flagged before the due date, not after.
Open orders vs in-transit
These two words get mixed up in many sheets. Keep them apart.
- Open order: Amazon has asked for the units, but you have not shipped them yet. The work is still on you.
- In-transit: you have shipped. The units are on the road or waiting to be received. The work is on the carrier and the receiving dock.
- Received: Amazon has taken them in. Only now are they Amazon's stock.
Planning on the Vendor side
Vendor planning is mostly about being ready. Look at Amazon's stock and its sales speed to guess what POs are coming and how big they will be. Then check your own stock and your supplier dates against that guess. If a large PO is likely in three weeks and your factory needs five, you are already behind, even though no PO exists yet.
Watch the PO window as well. A PO has a delivery window, and stock that arrives after it may be refused or rescheduled. So the date that matters is not when you ship but when Amazon can receive. Build the dock appointment and transit time into the plan.
Seller and Vendor on the same product
Many brands sell the same product both ways. That is fine, but the stock is in two different places with two different owners. Seller stock is yours and you can move it. Vendor stock is Amazon's and you cannot. Treat them as two lines for the same product, each with its own cover, its own lead time and its own next action.
| Seller (3P) | Vendor (1P) | |
|---|---|---|
| Who raises the order | You | Amazon, with a PO |
| Stock now | 200 units yours at Amazon | 300 units Amazon's |
| Asked / on the way | 40 units inbound | 500 asked, 400 confirmed, 150 shipped |
| Sales speed | 25 per week | 40 per week |
| Key number | Cover: 240 ÷ 25 = 9.6 weeks | Fill rate: 400 ÷ 500 = 80% |
| Action | No order yet; reorder point in about 3 weeks | Ship the 250 confirmed units still open; explain the 100-unit gap |
Seller asks 'when do I order?'. Vendor asks 'can I fill what is open?'.
Why one sheet for both breaks
A shared sheet usually adds up on-hand, inbound and sales into a single weeks-of-cover figure. That works for Seller. It breaks for Vendor for three reasons.
First, Amazon's on-hand is not yours to move, so cover on the Vendor side tells you what POs to expect, not what to send. Second, lead time starts at a different point: for Seller from your order to the supplier, for Vendor from the PO date. Third, the sales are different. Vendor sales are shipped to Amazon, Seller sales are shipped to customers, and totals that mix them hide both.
The fix is not a better formula. It is two views of the same product, each with its own trigger, side by side, so no one reads a Seller number as a Vendor one.
Do this weekly
- List every open PO with its due date and units; flag any you cannot fill.
- Compute fill rate per PO and per product for the last month.
- Keep open, in-transit and received in separate columns, never one total.
- For Seller, run the reorder point for every product.
- Look at Vendor and Seller side by side for products sold both ways.
- Chase every PO where the shipped units are lower than the confirmed units.
Quick questions
Can I use the same reorder formula for Vendor and Seller?
Not as is. For Seller the formula decides when and how much to send. For Vendor the PO decides, and your plan decides whether you can fill it in time.
What counts as a good fill rate?
It differs by category and by the buying team's expectations. Track yours monthly, find the POs that pull it down, and fix those first.
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Next step
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