Sellsy allows you to efficiently manage your orders with several deliveries by managing the remaining products of your order.
Important: this feature is only available for the products of your catalog.
Click on Settings then Documents settings.
From there, activate back orders management:
Creating an estimate with two articles, 10 units each:
Now creating a first delivery slip with a quantity of 3 for each article:
When we create the second delivery slip, only the remaining product are offered: