Have you signed into your Ticketmaster account lately? You may find you're in for a surprise.

Any Ticketmaster customer who has purchased tickets between Oct. 21, 1999, and Feb. 27, 2013, could be eligible for free ticket vouchers, a $2.25 discount on tickets or a $5 discount on shipping. The unexpected credit (for most of us, anyway) comes by way of a 13-year-old lawsuit against Ticketmaster over the fees it charged for ticket sales.

All you have to do is sign into your Ticketmaster account, head to your account and look for the section marked "Active Vouchers." If you're eligible for the credits, you should see them here.

There are, of course, some catches. For one, the vouchers aren't applicable to every event. Ticketmaster has an updated list of specific concerts to which vouchers may apply — you can find that list here. It's not that searchable or sortable, so be prepared to do some clicking around to find what you want. Also, the vouchers do have an expiration date of June 2020. So you can't sit on them forever.

The other main catch is that you probably can't use the vouchers quite yet. Ticketmaster first started putting the vouchers in people's accounts a few days ago, but then many users reported that they had disappeared. Ticketmaster told users on Twitter that the codes won't work or may not even be available until the final event list is set.

It's also unclear exactly how many vouchers Ticketmaster will award. Per the terms of the settlement, it has to pay out at least $10.5 million a year, and $42 million over four years. So, depending on how many people redeem their credits, Ticketmaster may have to release more free tickets.

Still, it's a credit most people probably didn't know they had coming. And, if you're looking for even more nice surprises, you should also check your Amazon account. (Amazon's chief executive, Jeffrey P. Bezos, is the owner of The Washington Post.) Many people have reported getting messages Tuesday letting them know that they have a credit on their accounts from the lawsuit between the U.S. government and Apple, over e-book prices. The credit, which you can find by heading to the "Gift Cards" section of your account, is valid for 12 months and is applicable to most goods, with the exception of gift cards and certain subscriptions.