Exhibit 23.3

Independent Registered Public Accounting Firm’s Consent

We consent to the inclusion in this Registration Statement of Multiplan Corporation on Form S-1 of our report dated January 29, 2020, except for Note 8, as to which the date is February 12, 2020, which includes an explanatory paragraph as to the Company’s ability to continue as a going concern with respect to our audit of the financial statements of Churchill Capital Corp. III as of December 31, 2019 and for the period from October 30, 2019 (inception) through December 31, 2019, which report appears in the Prospectus, which is part of this Registration Statement. We also consent to the reference to our Firm under the heading “Experts” in such Prospectus.

/s/ Marcum llp

Marcum llp

New York, NY

October 30, 2020