Twitter and American Express have worked together in the past to invite small businesses to the social network’s self-serve ad platform. The two companies have partnered again to launch a new coupon campaign.

Through this promotion, AmEx members can link a merchant coupon to their credit card by tweeting a hashtag from a retailer — which is similar to the one the company has with Facebook.

In order to participate, consumers have to sync their credit cards to their Twitter accounts. Once the hashtag has been tweeted, the individual can redeem their offer with a purchase using the synced card. The discount will be applied to the card — no printing required.

American Express has created a new Twitter account — @amexsync — that will confirm enrollment and notify participants if an offer has expired. It’s important to note that the only confirmation is an @reply message from American Express. It’s recommended that consumers favorite that tweet for easy access.

This type of promotion can pull in a lot of exposure and help to bring in new customers. The only downside is that small businesses can’t participate yet. Currently it appears to be limited to national brands, including H&M, McDonalds, Whole Foods, and so on.

[Via: GigaOm, Image credit: Dennis Hill]