Amazon Replenishment Software: How to Choose One, and How to Test It Before You Trust It

Written by the BidVentor Editorial Team. Reviewed by Adeel Imrani, founder of BidVentor (14 years growing a $2M beauty brand on Amazon, $30M+ ad spend). Last updated November 2026.

Quick answer

Amazon replenishment software tells you which FBA SKUs need more stock, how many units to send, and when to ship them so they arrive before you run out. The good tools do three things a spreadsheet struggles with: they count inventory already on the way on the day it actually lands, they use your real lead times instead of a guess, and they put a date and a dollar figure on every stockout risk so you fix the expensive one first. Before you trust any tool, run a two-week shadow test: let it predict stockout dates while you keep restocking your usual way, then compare its predictions to what really happened. A tool that cannot pass that test will not save you money, however good the dashboard looks.

Key takeaways

• A stockout costs you twice: the sales you miss while the shelf is empty, then the ad spend it takes to climb back in rank.
• Amazon says that from February 1, 2027 the low-inventory-level fee will apply only when inventory falls below 28 days of supply, measured on actual shipments in the four weeks before and after the assessment date. Running thin will still cost money.
• Judge replenishment software on six tests: inbound handling, lead-time inputs, dollar-ranked risk, capacity limits, confirm-first control, and history of past stockouts.
• A two-week shadow test tells you more than any demo.
• Replenishment and advertising are one decision. Ads that send traffic to an empty listing are pure waste.

Why sellers go looking for replenishment software

Most sellers start with Amazon’s own restock report and a spreadsheet. That works while you have a handful of SKUs and one supplier. It starts to break in three predictable ways.

The sheet says what is low, not when it hits zero. A list of “low” SKUs does not tell you whether the problem lands in four days or forty. Without a date, every low SKU looks equally urgent, so the one that pays your ads gets the same attention as a slow seller.

Inbound gets double counted or ignored. A shipment that left your warehouse last week is not sellable stock yet. Count it too early and you think you are safe when you are not. Ignore it and you over-order.

Lead times drift and nobody updates the cell. Your supplier quoted 30 days in spring. Now it is closer to 45, plus Amazon’s receiving time. The spreadsheet still says 30, and every reorder point it gives you is two weeks late.

Seller forums tell the same story about the cost of getting it wrong. Out of stock for a few weeks, and the listing behaves almost like a new launch: rank slides, organic sales fall, and you pay for clicks to win back the position you already had. That recovery cost rarely shows up in any report, which is why stockouts feel cheaper than they are.

The 2027 low-inventory-level fee change, in plain English

Amazon charges a low-inventory-level fee on FBA products that run low on stock relative to sales. Today it is assessed using trailing 30-day and 90-day sales. In its 2027 fee update, Amazon says that from February 1, 2027 the fee will apply only when your inventory falls below 28 days of supply, based on actual shipments in both the four weeks before and after the assessment date.

What that means for planning:

1. 28 days of supply is now the line to watch. Your replenishment tool should show days of supply per SKU, not only units on hand.
2. Demand spikes should trigger it less often. Because Amazon also looks at the four weeks after the assessment, a one-off spike or an end-of-season product is less likely to be charged. Steady sellers that run thin are still exposed.
3. Too much stock is its own cost. The same update folds aged inventory charges into a single age-based storage rate. The goal is a band: enough supply to clear 28 days, not so much that units age.

Good replenishment software turns that band into a ship-by date for each SKU. A tool that only tells you to “send more” pushes you toward the storage problem instead.

Six tests to run on any Amazon replenishment software

Use these in every demo and trial. Each one is a yes or no question, so you can compare tools quickly.

1. Does it count inbound on the day it arrives?

Ask how in-transit shipments are treated. The right answer is that a shipment counts from its expected arrival date plus Amazon’s receiving time. Then ask the harder question: if a shipment lands after you run out, does the tool still show the gap? Many tools quietly add inbound to on-hand stock and hide a stockout that is coming in the meantime.

2. Can you give it your real lead times, case packs and minimum order quantities?

A forecast is only as good as its lead time. You should be able to set lead time, case pack and MOQ per SKU, ideally by uploading one file. If the tool uses a default for everything, its reorder dates will be wrong for your slowest supplier, which is usually the one that matters.

3. Does it rank risk in dollars, not just units?

Twenty units short on a high-margin hero product is worse than two hundred short on a filler SKU. Ask whether the tool shows sales at risk and profit at risk for each SKU, and whether the list is sorted so the most expensive problem sits on top.

4. Does it respect your FBA capacity limit?

Your plan has to fit the storage capacity Amazon gives you. A tool that recommends more cubic feet than you are allowed creates a plan you cannot ship. Look for plans sized against your limit, with a clear note when the limit caps a SKU.

5. Do you confirm before anything is created?

A replenishment tool should build the plan and wait for you. It should not create shipments, buy labels or confirm anything in Seller Central on its own. Confirm-first control matters most in your first months, while you are still learning whether to trust the numbers.

6. Does it show what past stockouts cost you?

History is the honest test. A tool that lists your stockouts from the last couple of months, with the sales they cost, shows whether its math matches reality. It also gives you a baseline to judge it against later.

The two-week shadow test

Demos use clean example data. Your account does not look like that. So before you change how you restock, run the tool in the shadow for two weeks.

1. Day 1: Connect the tool and upload lead times and unit costs. Write down its predicted stockout date for your top 15 SKUs by revenue.
2. Days 1 to 14: Keep restocking exactly as you do now. Do not act on the tool’s advice yet.
3. Day 14: For each of the 15 SKUs, compare the predicted date against your actual days of supply. Note any SKU it flagged that you missed, and any SKU it flagged that was never at risk.
4. Decide: If the tool caught real risks you missed and its false alarms were few and explainable (for example, a supplier lead time you had not entered), it has earned a trial with real decisions. If its dates were far off and you cannot explain why, stop there.

A worked example (illustrative)

Here is how that plays out for a made-up seller with three SKUs. The numbers are for illustration only.

SKU	Units on hand	Daily sales	Inbound	Lead time	What a basic sheet said	What a date-based tool said
Hero serum	300	15	400, arriving day 25	35 days	Fine, 700 units counting inbound	Runs out on day 20, five days before inbound lands. Ship-by date already passed, so send a bridge shipment now
Travel kit	900	6	None	30 days	Low priority	150 days of supply. Do not send more, aging risk
Refill pack	120	4	None	45 days	Low priority	Runs out on day 30, inside the 45-day lead time. Reorder today

The basic sheet treated inbound as stock in hand and missed the hero serum gap, which is the SKU paying for most of the ads. The date-based view caught it, told the seller to stop sending the travel kit, and flagged the refill pack because its lead time is longer than its runway.

Common mistakes when buying replenishment software

• Buying for the forecast chart. A beautiful forecast does not help if inbound and lead times are wrong. Test the inputs first.
• Skipping the unit cost upload. Without costs, “profit at risk” is an estimate. Most tools let you add costs later, so do it in week one.
• Letting ads run into an empty shelf. When a hero SKU is days from zero, scale its ads down and protect the budget. We cover that in our guide to reducing wasted ad spend on Amazon.
• Planning Q4 with summer lead times. Carriers and Amazon receiving both slow down in peak season. Our Q4 PPC strategy guide covers the ad side of peak season. Plan stock on the same calendar.
• Treating every alert as equal. If a tool cannot rank by dollars, you will chase the loudest SKU instead of the costliest one.

How BidVentor approaches replenishment

We built BidVentor’s replenishment tools around the six tests above. Stockout Guard reads your FBA inventory, sales speed and shipments already on the way from your Amazon reports. Every FBA SKU gets a stockout date, sales and profit at risk, and a ship-by date based on your own lead times, sorted into three tiers: out of stock now, runs out within lead time, and safe. It also shows past stockouts from the last 60 days and what they cost. Plans are sized against your storage limit, and nothing is created in Seller Central until you press Create Amazon inbound plan. It uses your seller account only, so you do not need Amazon Ads to use it.

Replenishment Autopilot is coming soon. It will compare inbound shipping costs and decide when a restock is large enough to be worth shipping.

Two other BidVentor tools sit next to replenishment. Fee Sentry flags Amazon fee overcharges and prepares claim drafts, which is useful when you are watching fee changes like the 2027 update. And the Amazon Ads Profit Machine keeps ad spend away from SKUs that cannot convert, because profitable traffic is wasted if FBA is empty. Its 4X ROAS guarantee applies to PPC only, and terms apply.

You get one free analysis after you sign up, so you can run it against your own account before you change anything.

When a spreadsheet is still enough

Replenishment software is not for everyone. If you sell fewer than about ten FBA SKUs, use one supplier with steady lead times, and check stock every week, a well-kept spreadsheet plus Amazon’s restock report can do the job. Add one column for days of supply and one for ship-by date (stockout date minus lead time), and you have most of the value. Move to software when you start missing ship-by dates, when inbound timing gets messy, or when you cannot tell which stockout would hurt most.

Frequently Asked Questions

What is Amazon replenishment software?

It is software that reads your FBA inventory, sales speed and inbound shipments, then tells you which SKUs need more stock, how many units to send and when to ship so stock arrives before you run out. Better tools also show the sales and profit at risk for each SKU.

Is Amazon’s restock report enough?

For a small catalog with steady suppliers, often yes. The restock report suggests quantities, but it does not put a dollar figure on each risk or show what past stockouts cost you, so larger catalogs usually outgrow it.

How does the 2027 low-inventory-level fee change affect replenishment?

Amazon says that from February 1, 2027 the fee will apply only when inventory falls below 28 days of supply, based on actual shipments in the four weeks before and after the assessment date. Keep steady sellers above 28 days of supply without overstocking slow ones.

How long should I test replenishment software before relying on it?

Run a two-week shadow test. Record the tool’s predicted stockout dates for your top SKUs, keep restocking your usual way, then compare its predictions to what happened before you act on its advice.

Should I pause ads when a product is about to stock out?

Usually you should scale ads down rather than run full budget into a listing that will soon be empty. Protect rank with a lighter budget, restock, then scale back up once inbound lands.

Sources and further reading

• Amazon Selling Partners: Update to US Referral and Fulfillment by Amazon fees for 2027, including the low-inventory-level fee change.

Related guides

• Reduce wasted ad spend on Amazon
• Amazon Q4 PPC strategy for the holiday season
• Amazon PPC clicks but no sales: how to fix it

About the reviewer

Adeel Imrani is the founder of BidVentor. He spent 14 years growing a $2M beauty brand on Amazon and has managed $30M+ in ad spend. Read more on his author page.

How we make this content

These guides are written by the BidVentor Editorial Team and reviewed by Adeel Imrani. Where we cite Amazon features or numbers, we link to Amazon’s own documentation. We update guides when Amazon’s tools or our guidance change, and we describe BidVentor’s features as they work today. See our methodology, or contact us with corrections.