What year and version?

by invoice you mean vendor bill?  his invoice to you his customer is your bill.

Assembly items are used to combine inventory on hand into one unique item that you sell, typically you do not buy an assembly item.  If you are going to but an assembly item […]

Resolution for 'assembly item screen issue: 'I want to print an invoice and it tells me I have to select “I purchase this assembly item from vendor” before I can print.' available: Yes.

The assembly item screen 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 assembly item screen issue yourself by looking for a resolution described in the article. If it is a complex assembly item screen issue or you are unable to solve the issue, you may contact us by clicking here or by using other assembly item screen support options.

For more information about resolving issues related to assembly item screen in Quickbooks/QBO or to get support for the issue 'I want to print an invoice and it tells me I have to select “I purchase this assembly item from vendor” before I can print.', click the link below: