The Sun says Tanner is set to join Cardiff in a £50,000 deal.
Tottenham were close to snapping up the former Arsenal winger, 20, in January before the Isthmian League Premier Division side announced personal terms could not be agreed.
But Steve Morison's side are primed to beat competition from Spurs, Brighton and Swansea for Tanner's signature.
Tanner is currently undergoing a medical ahead of signing a three-year contract with the Championship club.
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