USPS News & Information

How to avoid underpayment when shipping with USPS

Endicia is committed to helping you streamline shipping. Accurately paying postage ensures the best experience for both you and your customers, as underpayment may delay delivery and result in your customer being charged for postage due.

These tips will help you avoid underpayment when shipping with USPS:

  • Match the label to the packaging. Paid postage labels should match the packaging. For example, Medium Flat-Rate packaging requires a Medium Flat-Rate paid postage label.
  • Round up on weights! Postage rates apply only up to the maximum weight of the rate (either the pound or ounce, where applicable). For example, if your package weighs 3 lbs. 4 oz., it must be rounded up to the 4-pound rate, since it is more than 3 pounds. This is true for all classes of mail—domestic and international.
  • Check the dimensions, as dimensional weight pricing (DIM) may apply for Domestic Priority Mail pieces above one cubic foot. Always enter the package dimensions to ensure accurate postage is calculated. Learn more here:

You can find more information on proper shipping techniques at

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