BOM lines can be valid or invalid, depending on the validity dates specified on the BOM lines. This is useful if you need to assign a different item number to a BOM version for a period of time.

For example, you might want to substitute a frosted lampshade for the standard white lampshade in the lamp BOM for the month of May. Or, if the sub-production required for a BOM version is not available, you might want to use a replacement component from the vendor instead.