Ings signed on an initial loan from Liverpool with an obligation to buy for £18million.
The permanent deal, on a four-year contract, will kick in on July 1, 2019, with a further £2m due if Ings plays a set number of games.
Ings signed on an initial loan from Liverpool with an obligation to buy for £18million.
The permanent deal, on a four-year contract, will kick in on July 1, 2019, with a further £2m due if Ings plays a set number of games.