A fee in the region of £30m is being discussed.
Sky Sports News understands the deal is “edging closer” but there is still work to do on the fee, structure of payments and add-ons.
The 18-year-old recently agreed in principle a new long-term contract with the Blues.
Hall, who has featured for England U21s, made his Premier League debut for Chelsea last season and went on to make nine appearances in the top flight.
