Follow the steps in How to download the Inventory ledger detail report in Amazon. The key point is to select detailed view as the report type, not summary. The summary report does not have shipment level data, so it can't be used for this comparison.

Set the date range wide enough to cover from when the shipment was shipped until it was fully received, then request and download the CSV.

Open the CSV and apply 3 filters to isolate the rows for the shipment you are checking:

Filtering on Receipts is important. The ledger logs many event types, such as adjustments and transfers, and you only want the units that were received against this shipment.

With the filters applied, add up the quantity column for the rows that are left. This gives you the total units Amazon recorded as received for that shipment ID and SKU.

Go to FBA Shipments, search the Shipment ID, and check Units Received. Click the arrow on the row to see each SKU. The 2 numbers should match.

Say ConnectBooks shows 200 units received for SKU B07L5D3QQ8 on shipment FBA1983XTV9D, and you want to check it against Amazon. You download the detailed ledger, filter column D to B07L5D3QQ8, column F to Receipts, and column G to FBA1983XTV9D. You get 3 receipt rows totaling 200 units across 2 days. That confirms the match, and it also explains why the units may have posted on 2 different dates.

Can I use the summary ledger report?

No. It doesn't have shipment level data. Use the detailed view.

Why do the received units show on different dates?

Amazon can receive a shipment over several days, so you may see more than 1 receipt row.

What if the numbers don't match?

Check that your date range covers the whole time from shipping to fully received. If they still don't match, reach out to our support team.