The bookmaker spent more than £20 million on advertising in 2015.
It has held informal meetings with a handful of agencies and is expected to invite three to pitch for the brief.
Bark & Bite, which has offices in Leeds and Manchester, is William Hill’s retained creative agency but William Hill is seeking extra firepower for a major nationwide campaign.
The appointed shop will not be retained beyond the project and may be expected to work with Bark & Bite.
William Hill hired Creature as its lead ad agency in 2014 but the pair parted ways after only one year.
The bookmaker has also worked with Fabula and BMB in the past.