Hi,
Your understanding of Individual Purchase Order is correct . A purchase requisition - Purchase Order - MIGO has to be done .The stock will reach your company as a Sales Order stock reserved for the particular sales order which you can check it once you do goods receipt in MIGO.The sales order stock cannot be assigned to any other sales order .
Hopefully the stock will be available in your outbound delivery for the TAB items. Revert back if any issues.
Regards,
SRK.