The deal to take Kai Havertz from Bayer Leverkusen to Chelsea has reportedly been signed for more than a week.
The 21-year-old playmaker has been heavily linked with a move to Stamford Bridge in recent weeks, and the Blues are understood to be on the verge of finalising an initial £71.3m deal which could rise as high as £89m.
Chelsea are working on the official confirmation of the transfer now and an announcement is expected in the near future.
Transfer expert Fabrizio Romano reports that the paperwork was signed nine days ago, with only formalities to be completed since then.
Should the add-ons be triggered then the deal will be Chelsea's record signing and their sixth of a busy summer transfer window.