18. Bidding on behalf of the buyer.

Accepting 'commission bids' — that is, bids placed by the auctioneer1 on behalf of an absent bidder up to a pre-agreed maximum — creates an obvious potential conflict of interest2 since the auctioneer is then acting for two parties whose interests are antithetical. Most auctioneers do accept commissions to bid for potential buyers and this will be unobjectionable only if the consent, actual or tacit, of the seller is obtained