City are willing to go to €65 million for the England international - a price which is satisfactory for Everton.
However, the sticking point is the sell-on percentage former club Barnsley are due.
The Tykes are due 15 per cent of any fee Stones is sold for and Everton are reluctant to pay it. Instead, they're insisting City cover that side of the deal.
It's claimed this is the major obstacle holding up negotiations.