We sell tie rod assemblies.
They consist of a center tube with two ball-joints screwed into the ends, three separate parts but in an assembly.
We sell the ball joints separately, but we do not sell the center tube separately as it only comes as part of the total assembly. But the ball joints each have a part number and we stock and sell those seperately.
We stock complete assemblies and we stock the two ball joint parts.
Sometimes, when we run out of ball joints, we remove the joint from one (or more) of the tie rod assemblies and sell it as a separate item. This depletes the inventory of tie rod assemblies. Later, when we have replenished the ball joint stock, if we get an order for tie rod assemblies, we screw ball joints onto the left over center tubes and sell them as assemblies.
This then depletes the stock of ball joints, without selling any of that stock number. We thought of kitting, but we don’t buy the parts separately as kits and the center tube does not have a part number.
How can we handle this in terms of book keeping and inventory control?
In order to properly account for this, you should set up a part number for the center tube. Create a BOM for the center tube plus the ball joints. When you have to take them apart then create a disassembly production order which will back fill the inventory of the center tube and the ball joints individually. When you get the ball joints back in, you will need to create a production order for the assembly. Then you will need to receipt the production order to produce the assembly again.
This is the only way I know of to properly account for the items.