This is a tactical post. Not a strategy piece. The strategy — that FBA supply limits become the binding operational constraint for large brands — is covered elsewhere. This is about one specific play you run when Amazon caps how much you can send, and you need more inventory in FBA than the cap allows.
The basic situation
Amazon gives you a supply limit for each SKU or product type. When you try to create a shipment that exceeds that limit, Seller Central blocks you. The shipment will not save. You get a "high supply" flag or an error message telling you the quantity exceeds your current limit.
For Our Place during Prime Day prep, the cap was 5,000 units per shipment creation window. The demand projection required significantly more inventory than that in FBA before the event started. Sending everything in one go was not an option.
The instinctive response to this problem is to file a case with Amazon and wait for a limit increase. That is the right long-term move, and the team did it — with documented missed sales projections attached to make the case. But case resolution takes time, limit increases are not guaranteed, and Prime Day does not wait.
The practical answer is the 50/50 split.
How it works
Instead of trying to send everything in one shipment, you divide the total allocation across two consecutive shipment windows. You send 50% now and allocate the remaining 50% for the following week.
The mechanics are straightforward. If you need 8,000 units of a SKU in FBA and Amazon's limit is 5,000 per send, you create a shipment for 4,000 this week and a second shipment for 4,000 next week. Neither shipment exceeds the 5,000-unit cap. Both shipments process normally.
What makes this work is that supply limits in certain configurations apply per shipment creation rather than as a rolling weekly total across all sends. By splitting into two separate shipment records created in different calendar weeks, you are working within the structure of how the limit is calculated — not circumventing it.
The team used a pivot table to manage this at scale for Our Place, aggregating units across all affected SKUs, splitting each SKU's allocation 50/50, and populating the two-week shipment schedule from there. This is important when you are managing 20 or more SKUs with simultaneous supply constraints — tracking it manually per SKU gets unwieldy fast. A single pivot table with columns for Week 1 allocation and Week 2 allocation keeps the math clean and auditable.
Timing the split
The split only works if the Week 2 shipment arrives at the FC before you need it. For Prime Day, this means you need to account for Amazon's inbound receiving timeline on top of the transit time from your warehouse.
If the event is three weeks out and transit from California to the destination FC takes five days, you have time to send two waves with a week between them and still have both receive in FBA before Prime Day receiving cutoffs apply.
If the event is two weeks out, the math gets tighter. Amazon typically stops receiving new FBA inbound for Prime Day purposes in the one to two weeks before the event as FCs focus on order processing. You need to know that cutoff date and work backward to confirm that a second-wave send will check in with enough buffer.
The failure mode here is sending the second wave too late and having inventory in transit while Prime Day is running. That inventory exists, it is technically yours, and it is completely unavailable to fulfill orders. Plan for an extra two to three days of FC receiving buffer beyond the documented cutoff, because Amazon's inbound processing speed during peak prep periods is slower than normal.
What to watch for
A few things that can complicate the split:
Warehouse throughput. Our Place's warehouses had a practical ceiling of 100 to 150 pallets per single processing run. For oversized items like Dream Cookers, that translates to a relatively small unit count per send. If you need 4,000 units of an oversized item in one shipment, confirm that your 3PL can actually process that quantity in the time window required. Sending the shipment instruction is not the same as having pallets on a truck.
Carrier detention. During Amazon's peak receiving periods, inbound trucks sometimes wait hours at FC docks before unloading. If your carrier charges detention, those costs can add up quickly. Document all delivery appointment confirmations and timestamps. Amazon will reimburse detention charges if you file a case with proper documentation — appointment time, actual unload time, carrier detention invoice.
Split-week supply limit behavior. Test this before Prime Day, not during. Create a small test shipment the week before your first Prime Day wave to confirm that Amazon's system is treating the two-week split the way you expect. If the limit is calculated differently than anticipated, you want to know that with two weeks to adjust, not two days.
When to use the 50/50 split
Use it when you have hit a per-shipment supply limit and cannot wait for a case resolution before the event. Use it when the event timeline allows for two waves with enough receiving buffer on both. Do not use it as a permanent workaround for chronic supply limit problems — file the cases, document the missed sales, and push for permanent limit increases through the proper channel. The split is a bridge tactic, not a system.
