Chelsea are continuing talks with Benfica about signing Argentina midfielder Enzo Fernandez.
The 21-year-old World Cup winner has a release clause of about £106m, having joined the Portuguese club in August.
If Chelsea agreed to that amount it would eclipse the existing record fee of £98m paid for Romelu Lukaku and add to the record total of about £270m spent by the new ownership last summer.
Discussions are ongoing about the size of the fee and structure of the deal.
Chelsea's interest in Fernandez continues a recent policy of buying young players with the hope their value will be maintained over the course of long contracts.
Under new chairman Todd Boehly, the club bought Aston Villa midfielder Carney Chukwuemeka, 19, for £20m in the summer and last month agreed a pre-contract agreement with 20-year-old Molde FK forward David Datro Fofana.
But paying more than £100m for the former River Plate player would be a huge outlay for Boehly, who is still involved in negotiations but has been helped by new technical director Christopher Vivell.
The move for Fernandez is being made with the contracts of 31-year-old midfielders Jorginho and N'Golo Kante coming to an end this season.
Kante has only made two appearances this season because of injury but while it is believed the France midfielder has a good chance of earning a new deal, the future of Italy's Jorginho is less clear.
Chelsea are eighth in the Premier League, seven points outside the Champions League places and with one win in their last five games in all competitions, while they are winless in their last five Premier League away matches.
Source: BBC