A year ago, Apple settled a giant class-action lawsuit (details below). The result was that millions of Americans got free credits in their accounts at Amazon, Barnes & Noble, or other e-book retailers. If you’re an American who is reading this article and you’ve bought e-books in the past, there’s a very good chance that you were included.

The catch? If they haven’t been used, all of these credits expire this Saturday at midnight Pacific time. So you’ll want to log in now and see if you have money waiting for you that will otherwise disappear in a matter of days.

Below you’ll find: (a) how to check your balance, (b) background on this whole affair, and (c) a bit more on an extra tactic I discovered that meant I was able to more than double the credit I had waiting for me. (Although, as you’ll see, I almost lost it twice!)

How to check your balance

Maybe you already knew that you had a credit, and you’re sure that you’ve already spent it. If so, fantastic–go read this instead. But if you want to check your account on Amazon to be sure, here’s what to do–along with an extra key step that will seem obvious, but only in retrospect.

  1. Go to this page on Amazon. You’ll find a page entitled “Information for 2016 Apple eBooks Antitrust Settlement.”
  2. If you’re not signed in already, you’ll be prompted to do so.
  3. Once you’re signed in, if you were awarded credits, you’ll see a display that provides your “Total Credit,” along with “Unused Credit” and “Expiry Date.” The Expiry Date should be June 24, 2017, in almost all cases.
  4. Very important final step: Most people have multiple email addresses, so it’s crucial to log out of your account, and then try to log back in using any other email address you might have been using between 2010 and 2012. Amazon wants you to use these credits–it’s a purchase that Apple is paying for, after all–but it can’t necessarily tie accounts together, and let you know if there’s money waiting for you in an account you don’t often use.

Adding that last step more than doubled my credit, solely because I’d forgotten that back in 2010 and 2011, I often used another email address to make purchases at Amazon.

For reasons you’ll see in the next section, while Amazon is the most important retailer to check, it’s possible you could have a credit with any retailer who sold e-books in the first half of this decade. I couldn’t find a similar one-stop page on Barnes & Noble, for example, but this page gives you more information on how it calculated credits, and you should simply be able to log into your account to see if you still have money waiting for you.

Background on the whole case

All of this goes back to 2009. Amazon’s Kindle had 90 percent of the e-book market, and Apple was trying to break in. Steve Jobs was still CEO, and he sent executives to try to work out a deal with some of the biggest New York publishers.

Basically, Apple offered to let publishers set their own prices on Apple’s platform, and agreed to take only a 30 percent cut. But Apple also required that the publishers agree not to sell to any rival (like say, Amazon or Barnes & Noble) for less. Overnight, some e-books that had been selling for $9.99 on Amazon rose to $12.99 or $14.99.

(As an aside, I paid special attention to this because one of my books, The Intelligent Entrepreneur, which came out in 2010, was affected by it. That experience is part of why I started writing e-books like How to Raise Successful Kids, and giving them away for free.)

Ultimately, the U.S. Department of Justice got involved, and there was a big lawsuit. In the end, Apple agreed to pay $400 million in total to “millions” of people who bought e-books at inflated prices. These were the biggest publishers, and a vast majority of books were sold on Amazon, so the odds are good that if you bought any big, best-selling book between the middle of 2010 and 2012, you were probably part of the lawsuit.

The extra tip

A year ago, I wrote about this settlement when it first came out, and when people started to get their credits. But I also mentioned that I’d realized that I had a second email account with Amazon back at the start of this decade.

Hence my zealotry on this idea: My first credit was $17.92; when I logged in under the second (older) email, I had another $21.17 waiting for me.

How’s this for irony, though? Despite all that, I actually forgot about the second email address and the second credit until this past weekend, when Amazon helpfully sent me a message reminding me that it was there, and that it was going to expire soon.

One more little trick for you: My wife and I had decided we were going to finally break down and get an Amazon Echo, so I thought I’d use the $21.17 toward it. But then I realized that my second account–the one with the unused credit–wasn’t signed up with Amazon Prime. Talk about a First World problem, but this meant if I wanted free shipping, my new Echo wouldn’t arrive for about five days.

I went down a bit of a rabbit hole trying to research how to merge two Amazon accounts, or at least transfer a credit from one account to another. Let me save you the trouble, in case you ever need to do this. There’s no way to accomplish this online, but if you call Amazon Customer Service at 1-888-280-4331, they can do it for you.

For security, you’ll need to have both email addresses, along with the first names listed on each account, and at least one address associated with it.