John Stones's proposed move from Everton to Manchester City is reportedly being held up by a clause relating to his former club Barnsley.
Pep Guardiola's side have been in hot pursuit of the acclaimed 22-year-old centre-back this summer and are believed to have met the Toffees' £50m valuation of the England international.
According to the Sunday Express, however, discussions have hit a sticking point over the sell-on fee due to Stones's childhood club Barnsley, who are entitled to 15% of the transfer figure when he eventually departs Everton.
Both parties are haggling over who should pay the fee, meaning that Stones could eventually be sold for almost £59m if Everton win the argument.
That transfer figure would make Stones City's club-record signing, topping the £54m paid for Kevin De Bruyne last summer.