The 21-year-old is currently with the national team and was an unused substitute as Germany drew 1-1 with Spain on Thursday. He was expected to feature in some capacity against Switzerland until he was required to head to London for a medical.
Leverkusen confirmed the news via a social media post which read:
"Kai Havertz has left the Stuttgart headquarters of the German national team to clarify matters surrounding a potential move to Chelsea. This took place after a discussion with Bayer 04 and DFB leadership."
Having been under a transfer ban last summer, Chelsea are making up for lost time ahead of the 2019/20 campaign as they have spent £136m on Hakim Ziyech, Timo Werner, and Ben Chilwell so far.
The fee for Havertz is believed to be around an initial £72m with the potential for add ons which would Chelsea's spending for the summer beyond the £200m mark.
Over the past year the rumours linking Haverzt with a move away from Leverkusen intensified, particularly during his form after lockdown. In 2019/20 he contributed to 27 goals via 18 scored himself plus nine assists, and eventually reached a 95 FC Rating for his performances.
Real Madrid and Bayern were considered the leading contenders for his signature previously, but Chelsea have won the race should there be no complications with the medical.
Chelsea have also signed Thiago Silva and Malang Sarr on free transfers this summer, and are still in the market for a goalkeeper to compete with or possibly replace Kepa Arrizabalaga.