One extremely popular Amex Offer is back once again. Under this promo, when you spend $100 or more using your enrolled American Express card either online or in-store at Staples, you’ll receive a one-time $20 statement credit. This offer is good through August 31, but enrollment is limited. The last time this promo was available, max enrollment was reached in less than half a day, so you’ll want to sign up as quickly as possible.

Update 7/22/15: In what must be record time, this offer reached max enrollment in just a few hours after this post went live.

To sign up for this offer through Twitter, tweet using #AmexStaples. E-gift card purchases, B2B sales at StaplesAdvantage.com, as well as certain other exclusions do apply–see this page for full terms of this offer. As usual with these Amex/Staples deals, however, there are no exclusions on the purchase of regular gift cards.

To take advantage of this offer through Twitter:

1. You must first have an American Express card connected with Twitter (see sync.americanexpress.com/twitter for more details on how to connect your Card)
2. Tweet using the hashtag #AmexStaples
3. Receive a response message through Twitter from @AmexOffers stating that this offer has been added to your connected Card
4. Then, use your synced card to spend at least $100 at Staples in-store or online by August 31, 2015

If you don’t have a Twitter account and don’t want to create one, you may also be able to find this promo through the other Amex Offer channels:

• Your AmericanExpress.com account – Log into your online account and click on the “Amex Offers For You” tab.
• Use the American Express iPhone App and visit the ‘Offers For You’ tab in the ‘Membership’ section
• Through Facebook at amex.co/facebook

You can also find a full list of other publicly available Twitter / Amex Offers here.

If you’re not already familiar with Amex Offers and want to learn the basics of the program–including how to sign up for offers–see this guide.