By Paul McBeth
The Commerce Commission has delayed its decision on whether to approve Z Energy's application to buy Chevron New Zealand's service station chains.
The decision, which was due today, will now be made on April 29.
The delay will add about $10 million to the cost of the acquisition.
The regulator previously flagged an extension was possible given the complexity of the merger, while Z has said any delays past the November 30 cut-over date would cost it about $2 million a month.
"We are still continuing to assess the competition effects of the proposed merger in a number of markets," the commission said.
Z wants to buy the Caltex and Challenge! branded chains for $785m, giving it 49 percent of the retail market.
Rivals have made submissions against the deal which has received Overseas Investment Office approval, and the commission's decision is its final regulatory hurdle.
Z's shares last traded at $6.70, and have climbed 45 percent this year.