He said Wonder had waived the rights until "way after the wedding," The Daily Telegraph reported.
The singer said he was "incredibly happy" for the couple and was "absolutely sure" his friend, the late Princess Diana, "would have loved the whole thing. I really hope she would have loved this track. I have a feeling she would have done."
Earlier, Michael told his Twitter followers: "I want Will and Kate to know that this a genuine gift, not a promo exercise."
Michael said he was not "angling" for an invitation to the April 29 wedding, and the royal couple should be "surrounded by people they love, not dodgy ex-con pop stars."
The singer was given an eight-week prison sentence last year after crashing his Land Rover while under the influence of marijuana.