Reservations in Microsoft Dynamics 365 Business Central can block new sales orders even when you have enough physical inventory. The quantity is already committed to other orders.
When you enter a quantity on a sales order line, the assigned quantity field shows how much Business Central can actually reserve. If part of the stock is already reserved for other orders, auto-reserve fails even though the graphical inventory profile looks fine.
To see what blocks a reservation, open the item list and look at the reservation entries for the specific item. This gives you the full list of reservations across all sales orders, so you can decide which ones to adjust.
Why reservations block new orders despite available stock
The reservation functionality in Business Central has one recurring challenge: figuring out flexibly whether a quantity is actually possible to reserve or not.
Take a concrete example. You enter 13 on a sales order line. The assigned quantity field shows that the system did assign 13. But when you look closer, it turns out the full amount is not possible, because part of the stock is already reserved for other orders.
If you check the graphical profile for the sales order line you just entered, everything looks fine. You have enough of the item on hand. The problem is that the inventory is already committed elsewhere through existing reservations.
How to confirm a reservation is not possible
To verify the situation, go into the reservation entry and try to auto-reserve. Business Central will tell you it is not possible. The available stock is there, but it is locked to other demand.
Changing an existing reservation in this scenario is genuinely complex. With the standard functionality, you have limited visibility into where the conflict comes from.
Use reservation entries on the item to see the full picture
The practical way to investigate is to open your item list and look up the reservation entries for the specific item.
This gives you a complete list of all reservation entries for that item, including the reservations tied to many different sales orders. From here you can select individual entries and see exactly what is committed where.
That overview lets you assess whether a new reservation is possible or not, instead of relying only on what the reservation entry on a single sales order line tells you.
Q&A
Why can’t I reserve stock even though the item is in inventory?
Because the available quantity is already reserved for other sales orders. The graphical profile may show enough stock on hand, but if it is committed to other demand, Business Central cannot assign it to your new order.
What does the assigned quantity field tell me on a sales order line?
It shows how much of the quantity you entered the system was actually able to reserve. If you enter 13 and only part of the stock is free, the assigned quantity reflects what could be reserved, and auto-reserve will report that the full amount is not possible.
How do I see all reservations for a specific item?
Open the item list and look up the reservation entries for that item. This shows every reservation entry across all sales orders, so you can identify which orders are holding the stock and decide what to adjust.