Do You Earn Rewards on Shipping Supplies and Packaging?
Supplies versus postage
There are two different things here. The physical packaging, boxes, tape, mailers, bubble wrap, is a retail purchase, while the postage to actually send the package is a shipping-carrier charge. They can code differently, so buying supplies and paying postage in one visit may earn two different rates. Postage coding is covered in shipping and postage rewards.
Office stores can trigger a bonus
Packaging supplies bought at an office-supply store often ring up under the office-supply category, so a card with an office-supply bonus earns its higher rate, as explained in office supply store bonuses. The same tape and boxes from a shipping carrier counter or a big-box store usually code as that merchant instead and earn the base rate.
The best card for packaging
If you ship often, buy supplies at an office store on an office-supply-bonus card, and put postage on a card that rewards shipping. Otherwise a strong flat-rate card covers both fine. Run your spending through the rewards calculator and compare options in best cash back cards.