Amazon inventory management: reorder points, safety stock and the UK FBA rules that set your limits

Inventory decides more Amazon profit than most founders realise, and it does it quietly. A stockout costs the sales you miss and, in our experience, much of the rank the product took months to earn. Overstock costs storage, then surcharges, then the cash you could have spent on the products that are selling. The job is to keep every product between the two, on purpose, using numbers you already have.

This playbook starts with the UK FBA rules that set the edges, because several of them have changed since our older posts were written. Then it covers forecasting, days of cover, reorder points, multichannel replenishment and when to stop replenishing a product altogether.

The UK FBA rules that set your limits

All fees below were checked on Seller Central UK on 1 October 2026.

What is the Amazon IPI score?

The Inventory Performance Index (IPI) is Amazon’s score for how efficiently you manage FBA inventory over time³. It still applies in the UK, and Amazon uses it as one input to your capacity limit¹⁵. Amazon names four areas that move it³:

A few details from Amazon’s IPI FAQ are worth knowing¹⁵. Only Professional sellers with stock at Amazon and recent activity get a score, so a seller new to FBA, or inactive for 13 weeks, may not have one. New ASINs don’t affect it in their first 90 days, and stock you have asked Amazon to remove or liquidate drops out of it. The score blends recent and long-term performance, so improvements take time to show. Amazon’s UK pages don’t publish a score range or a minimum score³¹⁵.

Capacity limits and IPI

Amazon sets your capacity limit from your IPI score and other factors: sales history, seasonal peaks, forecasts, new products, scheduled deals, fulfilment centre capacity and shipment lead time¹. If stock on hand plus stock in transit would exceed the limit, you cannot create the shipment. New Professional accounts active for less than 39 weeks have no limit while they build a sales record¹.

Two tools give you room. Capacity Manager lets you bid a reservation fee for extra space; there is no upfront payment, and you earn a £0.15 performance credit for every £1 of sales made using the extra capacity¹. Capacity relief lets you send stock even when you are at your limit for products that are low or out of stock, enrolled in a deal, voucher or Prime exclusive discount, seasonal, or new to FBA in their first 90 days².

Our older replenishment post said the minimum IPI was 400. Amazon’s UK help no longer publishes a minimum score³, and storage overage fees, which used to make a low IPI expensive, have not been charged in the UK since July 2024⁴. IPI still shapes your capacity, so the habits it rewards still pay: selling through, fixing stranded listings and keeping popular products in stock³.

Storage, peak and the utilisation surcharge

Storage is charged on your daily average volume, so a bulky slow seller costs far more to hold than a small fast one. October to December rates are roughly double for standard-size products⁵, and peak fulfilment fees apply to many UK FBA orders from 15 October 2026 to 14 January 2027¹³. Send Christmas stock early enough to sell, not so early that it sits through two months of peak storage.

The storage utilisation surcharge is worth understanding because it is, in effect, a weeks-of-cover test. Amazon divides your average daily inventory volume by your average daily shipped volume over 13 weeks, then by seven. Above 22 weeks, Professional sellers who have used FBA for more than a year, with at least 0.71 cubic metres of stock in that size tier, pay a surcharge on top of storage for everything aged over 30 days⁵. Keep account-level cover under about five months and it does not apply.

The aged inventory surcharge

From 241 days, UK stock pays a monthly surcharge assessed on the 15th: £1.18 per cubic foot at 241–270 days, £3.14 to £3.41 up to a year, then £5.71 per cubic foot or £0.20 a unit (whichever is greater) at 366–455 days and £6.14 or £0.25 beyond that. It is charged on top of storage. A removal or disposal request submitted before the assessment date avoids it, and Amazon asks that removed ASINs are not restocked for eight weeks⁶.

The low-inventory fee, in the UK

Our 2024 post advised holding eight weeks of stock to avoid Amazon’s new low-inventory fee. For UK sales that advice no longer applies. The low-inventory cost coverage fee covers standard-size Pan-EU products sold in Germany, France, Italy and Spain when both 30-day and 90-day days of supply fall below 28 days, and orders placed in the UK store are exempt⁷. If you use Pan-EU, keep 28 days as a floor for those products.

Inbound, removal and disposal

In the UK, box-level inventory placement splits eligible shipments across fulfilment centres at no additional cost¹⁰; our guide on how to send products to Amazon FBA in the UK covers the shipment workflow step by step. The inbound placement service fee described in Amazon’s US help has no equivalent page in Seller Central UK. Removal and disposal fees are charged per unit by size and weight⁸, and since 1 May 2026 they are charged as each unit is removed rather than when the whole order completes⁹.

Forecast demand from one number per SKU

A forecast for replenishment needs four inputs per product:

1. Base velocity. Units sold per day over the last 8–12 weeks, counting only days the product was in stock. Averaging across stockout days understates demand, and the next order is short again.
2. Seasonality. Last year’s sales by month, as an index against the annual average.
3. Planned events. Prime Day, Prime Big Deal Days, Black Friday, a voucher, a TikTok creator push.
4. Trend. Is the product growing, flat or fading?

Add every channel into the same forecast. Your factory makes one product, not an Amazon one and a TikTok one, so forecast total demand and allocate afterwards.

Days of cover and the cover band

Every product needs a band, not a single target. The floor is your lead time plus safety stock: below it, you will run out before the next order lands. The ceiling comes from Amazon: it treats more than 90 days of supply as excess and suggests 30 to 60 days of expected sales at FBA³, while the utilisation surcharge starts at 22 weeks and the aged surcharge at 241 days⁵⁶.

If your lead time from China is 60 days or more, those two ends do not meet at Amazon. That is why most of the brands we work with hold the bulk of their safety stock in their own or a third-party warehouse and top FBA up every two to four weeks.

Reorder points and safety stock

Notice where the safety stock comes from. If the lead time never varied, safety stock would be just 79 units. A week of uncertainty in production or freight triples it. Cutting lead-time variability, by booking production earlier or agreeing firm ship dates, is often cheaper than holding more stock.

Then check what the order costs to hold. An order of 60 days’ demand (1,200 units) plus the safety stock averages about 844 units on hand. At 0.05 cubic feet a unit, that is about £32 a month in storage from January to September and £64 in peak⁵. For a small item the fee is minor; the real cost is the cash, about £5,900 at a £7 landed cost, and the risk that slow units drift past 241 days. For oversize products the fees themselves start to matter, so run the same sum with your own dimensions.

Replenishing across Amazon, TikTok Shop and your own site

One pool of stock, several channels pulling on it. Our allocation rule, in order:

1. Protect Amazon cover first. A stockout there costs rank as well as sales, and rank is slow to rebuild.
2. Hold a separate buffer for TikTok Shop pushes. A creator video can empty a month’s stock in days. Ring-fence stock before a planned push rather than letting it drain your FBA cover.
3. Use your own site as the flexible channel. You can delay dispatch or take backorders there without an algorithm marking you down.

Multi-Channel Fulfilment lets one FBA pool serve other channels. Amazon describes it as fulfilling orders from outside Amazon, including your own website, and sortable items up to 45.72 × 35.56 × 20.32 cm and 9 kg can ship in unbranded packaging at no additional fee¹¹. In the UK, a 1.5% fuel and logistics surcharge has applied to MCF fees since 2 May 2026, and MCF fees rose by an average of 3.5% per unit from 29 May 2026, on single-unit orders for envelopes and parcels and on all oversize orders¹². MCF orders also count in the sales history Amazon uses to set your capacity limit¹. The trade-off: sharing one pool means every channel lives inside your Amazon capacity limit. Check TikTok Shop’s current UK fulfilment rules before routing its orders through MCF; our TikTok Shop vs Amazon guide covers TikTok’s own fulfilment options.

Link stock to advertising, too. When a product’s cover drops below its lead time, ease off ad spend so the remaining stock lasts until the next delivery arrives. When a product is heading past 90 days of cover, put it into a voucher or raise bids to turn stock back into cash before the surcharges start.

SKU rationalisation: when replenishment is the wrong question

Some products should not be reordered at all. Revenue will not tell you which: a product can turn over well and lose money once referral fees, fulfilment, storage, returns and the advertising needed to sell it are counted. Rank every SKU by contribution margin over the trailing 12 months, then sort:

• Heroes: good margin and volume. Protect cover and grow them.
• Fixable: good volume, poor margin. Fix the price, pack size, fulfilment cost or ad efficiency before cutting.
• Cash traps: poor margin, poor volume, tying up stock and attention. Discontinue.
• Strategic keepers: thin numbers but a real reason to exist, such as a range-filler a business buyer expects. Keep them deliberately, not by default.

Discontinue without throwing money away. Sell remaining stock through with a voucher or a bundle before it reaches 241 days, point shoppers to the variation or pack you are keeping, and compare removal, disposal and liquidation costs per unit before choosing⁸. For new branded products, the New Selection Programme (2026) makes liquidation free on the first 200 units for 120 days after your first inbound¹⁴, which lowers the cost of a launch that does not work.

You can see profit per product, after Amazon fees and advertising, with the Profit X-Ray. It is the quickest way to find the cash traps.

SKU count is a vanity metric. The same revenue on fewer, healthier products is a more valuable business.

A weekly inventory routine

1. Update the forecast with last week’s in-stock sales and any new events.
2. List every product below its reorder point, and raise purchase orders.
3. List every product below its FBA floor, and book shipments, using capacity relief where it applies².
4. List every product with more than 90 days of cover or any units approaching 241 days, and decide: promote, move to your own warehouse, or remove before the 15th⁶.
5. Check your storage utilisation ratio on the FBA dashboard against the 22-week line⁵.
6. Once a month, check next month’s capacity limit when it is announced and request more space through Capacity Manager if you need it¹.

Everything else can wait. Good inventory management is mostly the discipline of looking only at the products that have left their band, every week, before they cost you anything.