Hi,When ever you create any line item for BOM the valid to date defaults to 31.12.9999.But you can restrict this when you have an alternate material.If you activate change management, where you can find alternative dates where you can define the new material replaces the old material.So when you enter BOM with change number in change option the New Material with future validity date will be available & the current material will be available with the change over date.Hope this is your requirement. If not please reply.Regards,PPUser.