QB Issue Resolution:

you do not assign a class to an assembly item any more than you can assign a class to an item

classes track transactions, not items, a build is not a transaction

top right of the inventory adjust screen is a block to assign a class

inventory adjustments are out of the ordinary things, usually only necessary when you do a physical count

Resolution for Issue 'How do I assign a class to build assemblies and inventory adjustments?' available: Yes (Solved).
Source: Intuit Community forum.

How do I assign a class to build assemblies and inventory adjustments?: this issue or error code is a known issue in Quickbooks Online (QBO) and/or Quickbooks. Support for this issue is available either by self-service or paid support options. Experts are available to resolve your Quickbooks issue to ensure minimal downtime and continue running your business. First try to resolve the issue yourself by looking for a resolution described below. If it is a complex issue or you are unable to solve the issue, you may contact us by clicking here or by using other support options.

Support for Inventory
Quickbooks Repair Pro will resolve it efficiently and affordably. Guaranteed resolution of your issue, or you pay nothing!

Error Recovery for Inventory [Canada]
E-Tech is the #1 Quickbooks data migration and Conversion service provider.

Get 50% off Quickbooks Online

Click Here for 50% off!

Additional Support Options: