title_body: Is it possible to cap royalties for an ebook?
upvoted_answer: I feel sure you could LEGALLY, it's just a matter of contract, but I doubt any publisher would want to fool with such a complicated setup. I might be wrong though. Possibly you might find one who'd be willing to do a contract where, if your total royalties from them exceed some fixed cap (it would need to stay fixed - asking to let you change the cap monthly is unreasonable) the excess would go into promotion, might be doable. Alternately, you could simply spend that amount directly promoting your books yourself, and not bother the publisher. Then it would be a deductible business expense I'd assume and so wouldn't be "income". That is probably the simplest thing.