Also, you're limited to $ 10,000 in purchases per year, but can purchase an additional $ 5,000 worth of these bonds if you use your tax refund to buy them. (gobankingrates.com)
Note, however, that the bonus cash back does include a strict cap of $ 3,000 of purchases per year in each category. (creditcards.com)
The 5 % applies to the first $ 25,000 in combined purchases per year - any spending after that will yield just 1 % back. (valuepenguin.com)