The statutory definition, and why it settles the question. Title 39 of the United States Code governs what may be sent through the mail, and section 3001(k) defines its terms before it prohibits anything. It says that "the term 'sweepstakes' means a game of chance for which no consideration is required to enter." Consideration is the legal word for what you give up to take part. A promotion that requires you to pay in order to enter, or to pay in order to collect, is therefore not a sweepstakes at all within the meaning of the statute, and the FTC states the consumer version of the same point flatly: "Real prizes are free", and "it's illegal for someone to ask you to pay to increase your odds of winning."
The mailing rules are specific, and they are a checklist a genuine promotion has to satisfy. Section 3001(k)(3)(A) makes a mailing nonmailable if it includes sweepstakes entry materials and fails any of a list of requirements. The mailing, the rules and the entry form must each disclose that no purchase is necessary to enter, and that a purchase will not improve the entrant's chances. All terms and conditions must be stated. The sponsor or mailer must be identified with a principal place of business or a contact address. The rules must state the estimated odds of winning each prize, the quantity, estimated retail value and nature of each prize, and the schedule of any payments made over time. And the mailing is nonmailable if it represents that people who do not buy may be disqualified from future sweepstakes mailings, if it requires an entry to be accompanied by an order or payment, or if it "represents that an individual is a winner of a prize unless that individual has won such prize."
That last item deserves a sentence of its own. Telling someone they have won when they have not is not merely dishonest; it makes the mailing nonmailable matter under federal law.
The lookalike check has its own rule, and it is the most concrete tell in the whole area. The statute defines a "facsimile check" as matter that "is designed to resemble a check or other negotiable instrument; but is not negotiable", and then makes a mailing nonmailable if it "includes any facsimile check that does not contain a statement on the check itself that such check is not a negotiable instrument and has no cash value." So a promotional check that carries no such statement on its face is already outside what may lawfully be mailed. A check that a recipient is invited to deposit is a different and worse thing, and the mechanism there belongs to the overpayment scam.
The exception that proves the rule: skill contests may charge. The same subsection defines a "skill contest" as "a puzzle, game, competition, or other contest" in which "a prize is awarded or offered", "the outcome depends predominately on the skill of the contestant", and "a purchase, payment, or donation is required or implied to be required to enter the contest". So a paid entry is lawful where the contest is genuinely one of skill, which is why the statute then requires a skill contest mailing to disclose the number of rounds or levels and the cost to enter each one, that later rounds will be more difficult to solve, the maximum cost of entering all rounds, and the estimated number or percentage of entrants who solve it. The FTC's warning on the same point is practical: a skill contest "can ask you to pay to play", but entrants "might end up paying repeatedly, with each round getting more difficult and expensive, before you realize it's impossible to win or just a scam."
A right most people do not know they have. Section 3001(l) requires anyone mailing this kind of matter to "adopt reasonable practices and procedures to prevent the mailing of such matter to any person who" submits a written request to be left alone, either directly to the mailer or through a state attorney general who passes it on. The request can be made by the person themselves or "through a conservator, guardian, or individual with power of attorney", and the mailer must keep records permitting suppression of that name and address for five years from the request. For a household worried about an older relative buried in prize mail, that is a usable, statutory step rather than general advice.
The dressing, and the two tells that survive it. The FTC records operators claiming to be from the government, using "fake names like the 'National Sweepstakes Bureau,' or pretend they're from a real agency like the Federal Trade Commission", and its answer is that "the government won't call you demanding money to collect a prize." Where a mailing is involved there is a second, physical tell: the FTC advises checking the postmark, because "if your 'notice' was mailed by bulk rate, it means many other people got the same notice, too", which contradicts the premise of a personal win.
Scale, dated and attributed. In the FBI's 2025 Internet Crime Report, Lottery/Sweepstakes/Inheritance Fraud drew 5,623 complaints and $194,147,851 in reported losses. The age concentration is the striking part: 2,785 of those complaints came from people aged 60 and over, roughly half. And the comparison with its structural parent is worth noting, because it runs against expectation. Advanced Fee Fraud, as the FBI spells it, produced more complaints, 7,762, and a smaller loss, $155,910,852. The prize version reaches fewer people and takes more from each of them.