How to apply a code
Add your boxes to the cart, go to checkout, and enter the code in the promo field. If it is valid for your order, the discount is itemized in the order summary and the payment amount updates before you pay anything.
If a code is not valid for the order, checkout says why: expired, fully used, already used by you the maximum number of times, or short of the code's minimum order or minimum card count.
What a code can do
A code takes a percentage or a fixed amount off, and applies to the items it was created for. Separately, a code can carry a free-shipping flag, which zeroes the shipping charge regardless of the discount type.
If a discount takes a total down to a few cents, checkout rounds it to $0.00 rather than charging the residue, and an order that is genuinely free completes without a payment step.
Where codes come from
Snapshot issues codes through its own emails and promotions. There is no code marketplace, and a code found on a third-party coupon site may be expired or invalid for your order. The checkout check is the authoritative answer.