The Brazilian has been banned for 18 days by a disciplinary panel of the British Horseracing Authority, with six days deferred until January 3.
While the focus will be on Champions Day at Ascot, De Sousa will be on the sidelines and will also miss October 23-27 and October 29-November 3, with the big race at Flemington on November 6.
De Sousa picked up the suspension under the totting-up procedure, having been found guilty of using his whip above the permitted level on too many occasions within a six-month period.
He already had an interference ban which ruled him out of October 16, 18, 19 and 22.
De Sousa's agent, Shelley Dwyer, said: "As it was a referral it would be hard to appeal it, so it's just one of those things.
"There were a few rides at Ascot on the cards, but the main thing now is getting him out to Hong Kong so he can get there and ride on the 4th, which is a big meeting.
"Of course the Melbourne Cup was playing on our minds as well and that was stressing me a bit, so that's all good.
"As much as it is a pain missing Champions Day, it is what it is - that's the totting-up system. It's very difficult, though, as he's had over 900 rides and five whip bans, but they are the rules.
"He's lined up for Withhold in the Melbourne Cup, so we just hope he gets in, there is a back-up, but we'll just have to see."
Danny Tudhope will also miss Champions Day for the same reason.
He was handed a 21-day suspension, with seven deferred. The ban runs from October 19 to November 2.
Tudhope has ridden Laurens to her two most recent Group One victories, but her regular partner PJ McDonald is aiming to be back in the saddle in time for the big Ascot meeting.
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