If a UFC fight is cancelled before it starts, your bet on it is void and the stake comes back to you, as if the bet had never been placed. That is the standard rule type. The NSW Bookmaker Declared Betting Events Betting Rules (the NSW rule book), made under the Betting and Racing Act 1998 (NSW), write it down: any event cancelled before it begins is refunded (clause 5.1.10). So $40 on Fighter X at an illustrative $1.70 returns $40, not the $68 a win would have paid.
The harder cases are fights that go ahead in a changed form: a new opponent, a missed weight, a different number of rounds, or a bout stopped with no result. Your bookmaker's MMA rules decide those, so the rule types below are what to look for in them, alongside the general settlement rules in sports betting explained.
Rule types for changed and cancelled fights
The NSW rule book binds bookmakers licensed in NSW and authorised to take bets on sport. It has a boxing section but none for mixed martial arts, so its boxing clauses appear in the last column as written examples of each rule type, not as the rule that settles a UFC bet.
| What happens | Rule types you will find | The NSW rule book |
|---|---|---|
| Fight cancelled before it starts | Void, stake refunded | Refunded (5.1.10) |
| Fight postponed to another date | Void unless held inside the bookmaker's window | Boxing: refunded if moved to the next calendar day or later (5.2.1.1); general rule: 3 calendar days (5.1.6) |
| Opponent replaced | Bets on the original pairing void | Boxing: a substitute makes the bout abandoned, refunded (5.2.1.1) |
| Missed weight, fight goes ahead | Bets stand | No clause |
| Scheduled rounds changed | Every bet on the bout void, or only bets that depend on the rounds | Boxing: every bet void (5.2.1.2) |
| Venue changed | Void, unless the terms say otherwise | Void unless agreed (5.1.14) |
| No contest | Void, sometimes with bets already decided left standing | No clause |
| Result changed after the event | Ignored: settled on the official result at the time | Later changes ignored (5.1.11) |
When a fight is cancelled or postponed
Timing does not change the answer for a cancellation. An MMA bet on a fight dropped in fight week, at the weigh-ins or an hour before the card is void either way, and a void bet is settled as if it had never been placed. If you used a bonus bet, the bookmaker's bonus terms decide whether it comes back as a bonus bet and when it then expires.
A postponement turns on the window in your bookmaker's terms. If a bout moves from one Saturday's card to a card three weeks later, it falls outside both NSW windows and any short window in a bookmaker's terms, and the rescheduled fight opens as a new market. A bout moved later on the same card is the same fight on the same day, so no postponement rule reaches it.
Season-long and title markets work differently. A bet on a fighter to hold a title at the end of the year is a future. Futures are commonly all-in, as the NSW rule book is by default (5.1.1), so a withdrawal from one fight does not refund it. All-in betting explains the rule.
When the opponent changes
A late replacement commonly voids bets on the original pairing, because a head to head is a bet on a contest between two named fighters and that contest no longer happens. The NSW rule book's boxing section says exactly that: a substitute makes the bout abandoned and every bet is refunded (5.2.1.1).
Example: Illustrative prices. You have $40 on Fighter X at $1.70 against Fighter Y. Fighter Y withdraws and Fighter Z steps in. Your $40 comes back, and X against Z opens as a new market with X at, say, $1.30, where $40 returns $52 if X wins: $16 less than the $68 the original bet offered.
The old price does not carry over, and the new one is set for a different fight. Treat the replacement bout as a fresh decision, at its own price.
Missed weight and catchweight bouts
When a fighter weighs in over the contracted limit, the bout either goes ahead at a catchweight or is called off. Under the Unified Rules of Mixed Martial Arts (weight classes section), if a missed weight leaves the fighters in different weight classes, the heavier may be no more than 5 lb (about 2.3 kg) heavier than the lighter. A commission may also refuse a catchweight bout it sees as unsafe.
For betting, a catchweight bout keeps the same two fighters on the same card, so the common rule type leaves bets standing at the prices taken. If the miss gets the bout cancelled, the cancellation rule applies and stakes come back. If the bout's scheduled rounds change as well, the next section decides.
When the scheduled rounds change
A five-round bout can be cut to three, or a three-round bout lifted to five when a main event falls through. There are two rule types. Under the first, every bet on the bout is void, which is how the NSW rule book's boxing section reads (5.2.1.2). Under the second, only bets that depend on the rounds are void: over or under rounds, round betting and go the distance.
With illustrative prices, you hold $20 on over 2.5 rounds at $1.80 and $30 on Fighter X at $1.60. The bout is cut from five rounds to three, and X wins on the scorecards:
| Bet | Every bet void | Only round bets void |
|---|---|---|
| Over 2.5 rounds, $20 at $1.80 | Void: $20 back | Void: $20 back |
| Fighter X to win, $30 at $1.60 | Void: $30 back | Stands: $48.00 returned |
No contests, technical decisions and results changed later
Under the Unified Rules, an accidental foul that injures a fighter too badly to go on ends in a no contest if the bout is stopped before two of three scheduled rounds, or three of five, are complete. The rule text also allows a disqualification in that case. After that point it goes to the scorecards as a technical decision, with the partial round scored, for the fighter ahead. An intentional foul that ends a bout is a disqualification instead.
A no contest has no winner, so head to head bets on it are usually void. Some terms keep bets that were already decided before the stoppage:
Example: Illustrative price. A three-round bout ends in a no contest at 4:10 of round 2. Over 1.5 rounds was decided at 2:30 of round 2, so $25 on it at $1.75 returns $43.75 where decided bets stand, and $25 where every bet on the bout is void.
A technical decision is a result, so head to head bets settle on it. Whether it counts as a decision win in a method market, or as going the distance, is a question for the terms: the Unified Rules list it among decisions, but the scheduled rounds were not completed. Draws have their own rules, covered with worked returns in UFC betting in Australia.
A result can also change after the event: the Unified Rules allow a commission to review a decision when a protest claims a clear rule breach (rule 2). The NSW rule book settles on the official result as adjudicated and calls any later disqualification or other change irrelevant to bets (5.1.11), so under that rule type a settled bet stays settled.
Multis and same game multis with a cancelled fight
A void leg drops out of a multi, and the multi is paid at the combined price of the legs that won. The NSW rule book does this in clause 5.1.9, and it adjusts a drawn leg by the dead heat method, halving its price where two are tied. With illustrative prices, $20 on Fighter A at $1.50, Fighter B at $2.20 and Fighter C at $1.80, with A and C winning:
| What happens in Fighter B's fight | B's leg | Multi price | $20 returns |
|---|---|---|---|
| B wins | 2.20 | 1.50 x 2.20 x 1.80 = 5.94 | $118.80 |
| Fight cancelled | Void | 1.50 x 1.80 = 2.70 | $54.00 |
| Draw, refund rule | Void | 2.70 | $54.00 |
| Draw, dead heat rule | 2.20 / 2 = 1.10 | 1.50 x 1.10 x 1.80 = 2.97 | $59.40 |
| Draw where the draw was priced, or B loses | Lost | None | $0.00 |
If every leg is void, the stake comes back. The multi bet calculator reprices a multi with void or dead heat legs.
A same game multi built on one fight is different: every leg comes from the same bout, so a cancellation voids the whole bet. A no contest or a single void leg can void the whole thing or re-price it, depending on the bookmaker, because those legs were priced together rather than multiplied. Same game multi rules covers the rule types.
How to check your bookmaker's MMA rules
Read the rules before fight week, not after a withdrawal. In your bookmaker's MMA or combat sports terms, search for these words: cancelled, postponed, substitute or replacement, weight, rounds, no contest, draw and disqualification. Each one answers a row of the table at the top of this page.
If a replacement bout opens and you decide to bet on it, compare its price first. Online betting on it closes when it starts: the Interactive Gambling Act 2001 bans online bets on a sporting event once it has begun (s 10B and s 8A(3)).
B337 plays no part in a void: it is software, not a bookmaker, so it takes no bets and never holds your betting funds, and your bookmaker settles a cancelled fight under its own terms. When a replacement bout opens, comparing its price across bookmakers is the job B337's Terminal does for the sports and markets it carries, with prices from 40+ bookmakers across racing and sports; not every bookmaker prices every fight. Its prices are read on a repeating cycle, so check one in your bookmaker account before betting. A free account opens a limited view of the Terminal with live odds.
Risk: Betting involves risk. A refund only returns your stake, a new matchup comes at a new price, and there is no guarantee of profit. See responsible gambling for limits and support.