Rotating-category cards like Chase Freedom Flex and Discover it occasionally feature Amazon.com as a bonus category — typically 5% back for one quarter of the year, usually in Q4. Outside the bonus quarter these cards earn 1%, so they're a supplemental tool rather than a primary Amazon card.
Check each card issuer's quarterly bonus calendar every three months.
When Amazon is a bonus category, activate the quarter through the issuer's site.
Charge Amazon purchases to that card until you hit the spending cap (usually $1,500), then switch back to your default cashback card.
Cardholders who already carry a rotating-category card for other bonuses — activating an Amazon quarter is a free 5% boost.
Activation is required each quarter and the cap is real. Miss the activation and the bonus quarter earns 1% like everything else.