If your IPI has slipped under 400, the thing that actually hurts is not the number. It is the capacity limit that follows it, arriving in the same month you were planning to restock. We understand how that feels, because it usually lands on a seller who has done nothing wrong except grow.
The score is not a judgement of your business. It is Amazon measuring how efficiently you use their warehouse space, and it responds to a small set of inputs in a fairly predictable way. That is good news, because it means the recovery is mechanical rather than mysterious.
The Inventory Performance Index runs from 0 to 1,000, and 400 is the line that matters. Below it, Amazon caps how much you can send in. Seller Labs, Canopy Management and SellerApp all describe the same threshold and the same consequence in their 2026 guidance, which is why we are comfortable printing the number.
What the score is actually measuring
Amazon is not asking whether your products are good. It is asking whether the space you occupy is earning its keep, and the four inputs it uses are all versions of that same question.
This matters for how you fix it, because the score is a weighted rolling picture rather than a snapshot. A single good week does not move it, and a single bad week did not cause it. What moves it is changing the shape of your inventory and then leaving it changed long enough for the rolling window to catch up.
The four inputs, and which one moves fastest
The published components are consistent across every source we checked: excess inventory percentage, sell-through rate, stranded inventory percentage, and in-stock rate.
They do not respond at the same speed, and that is the practical part. Two of them are rolling averages, so they take weeks. One of them is a straightforward error you can clear this afternoon. If you are under 400 and restock season is close, the order you work in decides whether the score recovers in time.
- Stranded inventory. Fastest. This is a listing problem, not a stock problem, and it clears as quickly as you fix the listings.
- Excess inventory. Medium. You control it by removing or moving units, and the effect shows as the units leave.
- In-stock rate. Medium, but only if you have stock to send, which is the trap.
- Sell-through. Slowest, because it is a ratio measured over a rolling window and it cannot be hurried.
Stranded inventory is the one people miss
Stranded inventory is stock sitting in a fulfilment centre with no active listing attached to it. Amazon is holding your units, charging you to hold them, and cannot sell them, which is the worst possible combination for a score that measures whether your space earns its keep.
The reason it goes unnoticed is that nothing announces it. A listing gets suppressed for a content issue, a variation relationship breaks, a pricing error deactivates an offer, and the stock quietly becomes unsellable while the dashboard reports it as inventory. Sellers who have never checked the Fix Stranded Inventory page are often surprised by what has been sitting there.
Worth doing this first, because it is the only input where the fix is immediate and entirely within your control. Each stranded ASIN is usually one of a small number of causes, and the underlying listing problem is the real fix. Our guides on listings that show as currently unavailable and broken parent and child relationships cover the two most common ones.
Excess inventory, and the arithmetic people avoid
Excess inventory is stock Amazon judges you are holding more of than your sales rate justifies. It is the input that hurts most, and it is the one sellers resist fixing, because fixing it means admitting that units bought with real money are not going to sell at the price you wanted.
The part that will genuinely annoy you is that holding those units is not free while you wait. Storage is charged monthly, it rises for older stock, and it occupies capacity you would rather spend on the products that are selling. So the true comparison is not the discount against your target margin. It is the discount against the cost of continuing to store, and against what that space could be earning instead.
The options, roughly in order of how much value they preserve: run a sale or a deeper discount to move units at speed, use an outlet or liquidation route, create a removal order and hold the stock somewhere cheaper, or dispose of it. None of those feels good. Storing dead stock through Q4 feels worse in January.
In-stock rate punishes you twice
In-stock rate measures how consistently your products are actually available for the demand they have. Running out is a double cost, because you lose the sales and you lose score at the same time, and a lower score means a tighter capacity limit, which makes running out more likely next time.
That loop is why a capacity limit arriving mid-recovery is so difficult. It is also why we treat inventory planning as an account health question rather than a warehouse question. If you have already been through a stockout, getting your rank back afterwards is a separate piece of work and it is worth reading before you restock.
Sell-through is the one you cannot rush
Sell-through compares units sold against units held over a rolling period. There is no clever action that moves it this week, which is exactly why it is worth starting the other three immediately: they buy you the time that sell-through needs.
The honest framing is that sell-through improves as a consequence of the other decisions, not as a task of its own. Clear the stranded units, cut the excess, keep the sellers in stock, and the ratio moves because the denominator changed.
The timing that decides whether this matters
Capacity limits are recalculated monthly rather than continuously, and the sources above place the update in the final week of the month. That single fact changes how you plan a recovery, because work finished on the 3rd and work finished on the 27th land in the same review, while work finished on the 29th waits a full month.
So if a restock matters to you, the calendar is part of the fix. Getting stranded units cleared and removal orders created before that window closes is worth more than the same work done four days later.
What the score does not do
It is worth being clear about the limits, because a score people misunderstand causes its own damage. IPI governs how much you may store and send. It is not an account health metric, it does not appear in the account health rating, and a low IPI is not a policy violation. Nobody is going to deactivate a listing over it.
Equally, a high score does not protect you from anything else. It has no bearing on suppressions, policy warnings or the metrics that do carry enforcement, which we cover in the guide to ODR, LSR and VTR.
What we would do first if this were our account
- Open the stranded inventory page and count what is there. Most sellers under 400 find something, and it is the fastest available win.
- Fix the listing problem behind each stranded ASIN rather than relisting blindly, because a relist that repeats the original error strands the stock again.
- List every SKU flagged as excess, with the storage cost you are paying to keep it, so the decision stops being emotional and becomes arithmetic.
- Decide on each one this week, discount, remove or dispose, and act before the monthly recalculation rather than after it.
- Protect the products that are actually selling. A stockout on a strong ASIN costs more than the excess stock you are agonising over.
- Only then look at the score again, and expect it to move over weeks rather than days.
If the catalogue is large enough that this reads as a month of work, that is usually the point at which sellers ask us to do it with them. Our inventory management service is built around exactly this sequence.
Related guides
Common questions about the IPI score
What IPI score do I actually need
400 is the threshold every current source agrees on, and it is the line where capacity restrictions begin. Sitting just above it is not comfortable though, because the score moves with rolling averages and a normal seasonal dip can put you under without any decision on your part. Most sellers we work with treat 400 as the floor to stay clear of rather than the target to hit.
How quickly can the score recover
It depends entirely on which input is dragging it down. Stranded inventory clears as fast as you fix the listings, so that part can move within days. Excess inventory moves as the units physically leave. Sell-through is a rolling ratio and cannot be hurried at all, so a recovery that depends on it takes weeks. We would not promise a timeline on any account without seeing which of the four is actually the problem.
Does a low IPI hurt my account health rating
No. They are separate systems measuring different things. IPI governs storage and restock capacity, while the account health rating tracks policy compliance and customer experience metrics. A low IPI is not a violation and does not appear on your account health dashboard. It costs you capacity, not standing.
Is it worth paying to remove stock just to raise the score
Sometimes, and the way to decide is to compare the removal cost against what continuing to store the units will cost you between now and the point they would realistically sell, plus the value of the capacity they are occupying. If those units are blocking restock of a product that sells reliably, the removal usually pays for itself. If they are simply slow but healthy, it often does not.
Why did my capacity limit change when my score did not
Capacity is not calculated from the score alone. Amazon also factors in your projected sales, your sales history and the space it has available, and it recalculates monthly. So a limit can tighten in a month where your score held steady, which is frustrating but is not a sign that something new has gone wrong on your account.
Does using a third party warehouse fix this
It changes where the problem sits rather than removing it. Holding reserve stock outside FBA and sending in smaller, more frequent shipments does genuinely help both excess inventory and sell-through, because less capital is sitting in Amazon's warehouse at any moment. It also adds a lead time you now have to manage, and a stockout caused by a slow inbound shipment costs you more than the storage you saved.