Altru will not allow an active vendor record to be marked inactive or deleted. To complete the merge, select the vendor as the target constituent and the other organization as the source constituent. 

If both constituents were vendor records, follow these steps to make them inactive: 
  1. Choose one of the vendor records to mark inactive. If you have any active merchandise, Edit the merchandise and choose the vendor record that will remain active as the vendor. 
  2. Once all of the merchandise has been moved to the active vendor, go to the vendor to mark inactive. 
  3. In the left under Tasks, click Mark Inactive.