When sending a package USPS First-Class Mail (Letter), make sure to include enough postage.

 

If an order is a Letter package and weights more than 1 oz., you should include an Extra Ounce Stamp (or the equivalent if you are using digital postage and not stamps).

 

Typically, packages with 5 or more cards will need the Extra Ounce postage, but it depends on packaging materials you use and marketing materials you enclose. So, either include the extra postage for all 5+ card packages, or weigh them with a postal scale to ensure they are under one ounce.

 

If you don't use enough postage, the post office may charge the recipient to claim the package, or return it to you for insufficient postage, which makes for very unhappy customers. You may be charged for the additional postage, and your seller account may be disabled if you repeatedly fail to include the necessary postage.