An overlay is a tournament player’s best friend and a casino’s worst nightmare. When the number of players registered for a tournament is not enough to cover the guarantee of the tournament, then we have an overlay, meaning free money for the players.

The one thing that any tournament director dreads is organizing a tournament that costs the casino money. Obviously, once in a while mistakes will be made and small overlays are a fairly constant occurrence, especially in online tournaments. However, these ten overlays just might have cost someone their job.

10. Borgata WPT Championship

In April of 2014, Borgata hosted the WPT Championship with a buy-in of $15,400. The tournament featured a $5 million guarantee, which meant that at least 333 players needed to show up to cover the guarantee.

Unfortunately for Borgata, they were 5 players short as only 328 players registered. This produced a slight overlay of $80,000, which is not much compared to the actual guaranteed prize pool, but does account for 60% of the money Borgata made in rake from the tournament. In any case, an overlay in a WPT Event is a rare thing to see.

9. WCOOP 2010 Event #23

WCOOP is one of the biggest online tournament series, proudly hosted by PokerStars for almost a decade now. These tournaments are incredibly popular and it’s rare to see an overlay in any of them, even the most obscure ones.

However, in 2010, some players got pretty lucky when they registered for the $215 NL Hold’em 4-max Event with a $700,000 guarantee. Somehow PokerStars made a serious miscalculation in the expected amount of players and when registration closed, only 2,915 were registered, creating a $117,000 overlay.

8. Full Tilt Poker UKIPT Galway Main Event

In 2013, Full Tilt was back up and running, ready to introduce great new innovations and sponsor tournament series. They decided to start off with UKIPT Galway, which featured a €1 million guarantee Main Event. The €1,000 buy-in meant that at least 1,000 players needed to register to meet the guarantee.

Eventually, only 860 players showed up, marking the first time in history that a UKIPT Event had an overlay, which, at €145,000, was a pretty significant amount.

7. PokerStars’ Sunday Warm-Up

The Sunday Warm-Up is probably one of the few tournaments that never sees an overlay. Well, except for that one time that it had a massive overlay of $260,000! How could this happen in one of the most popular weekly tournaments with a $500,000 guarantee?

Easy! A significant amount of players in any given tournament comes from players who register late, but in April 7, 2014, a technical problem on PokerStars caused the tournament registration to close right after the tournament began, making those who registered for it before the start some of the happiest players in the world that day.

6. PokerStars Canada Cup Main Event

If the Sunday Warm-Up glitch in April of 2014 made some execs facepalm, May forced them to do it all over again, only this time it was in the live arena at the PokerStars Canada Cup Main Event.

The event featured a massive $2,000,000 guarantee with a $3,000 buy-in, meaning that the organizers were expecting at least 666 entries. Unfortunately, only 578 people registered, creating an overlay of $266,000. Hopefully it wasn’t the same guy who was responsible for both the Warm-Up and the Canada Cup Main Event because things like this tend to lead to unplanned performance reviews.

5. Ultimate Bet Online Championship Main Event

When Ultimate Bet was still considered a legitimate online poker room, tournament players could enjoy series offering millions in guaranteed prize pools and final tables with commentary from Phil Hellmuth. However, even in the golden days of 2006, UB managed to make a staggering blunder.

The Ultimate Bet Online Championship (UBOC) offered just ten tournaments with a $1 million guaranteed Main Event being the last on the list. The first nine tournaments were successful, but the Main Event attracted far fewer players than was expected, creating a $300,000 overlay. Another great addition to all that free money is that UB was still paying out withdrawals back then!

4. Unibet €750,000 GTD

When big operators like PokerStars make mistakes, it’s usually something unexpected, but when small online poker rooms like Unibet try to jump over their own heads, you kind of feel a train wreck coming.

For some reason, on April 25, 2011, Unibet decided to host a €320 two-day tournament with a €750,000 guarantee. Why they thought doing this 10 days after Black Friday was a good idea, we might never know. Anyway, just like many would have expected, the guarantee was never in danger of being met and the final overlay was €329,000, prompting Unibet to understand that they need to become somewhat successful before hosting major tournaments.

3. iPoker $1 Million GTD

The biggest overlay in online poker history was recorded in 2006 on iPoker. At that point only a few skins made up the iPoker network. Despite this, they decided to host a $1M guaranteed tournament with a $1,100 buy-in, presumably expecting a huge number of players.

Turns out iPoker’s calculations were just a bit off, as only 568 people registered for the tournament, leaving the network to pay an a huge $432,000 overlay.

2. ISPT Wembley Main Event

The International Stadium Poker Tour was supposed to be the series to eclipse all other series. However, as many people predicted, it turned out to be one of the biggest blunders in the history of tournaments.

In fact, a year before the tournament was to take place, the organizers were aiming for a field of 30,000 players playing on laptops at Wembley Stadium and a €20 million guarantee. When the cocaine wore off, they settled for a more reasonable €3 million guarantee and a regular live tournament format without 30,000 laptops.

Even with the scope of the tournament reduced so drastically, the guarantee fell short by almost €600,000 (~$650,000), making the ISPT a very profitable venture for those who actually showed up.

1. Seminole Hard Rock Poker Open

In 2013, the Seminole Hard Rock Poker Open was an incredibly successful event, which featured a $10M guarantee that was met with ease. Thanks to that success, the organizers decided to bring the tournament back in 2014. This resulted in the biggest overlay the poker world has ever seen. Anywhere. Ever. By far.

Only 1,499 entrants showed up, each putting up $5,300. This made up only $7,495,000, which meant that the overlay equaled $2.5 million, which is one hell of a miscalculation.