The US Postal Service has proposed a rule change for Parcel Dimension Compliance that could significantly impact online sellers who purchase postage through marketplaces and third-party shipping platforms.
If finalized, the rule would go into effect July 12, 2026 and require accurate package dimensions on commercial USPS parcels, regardless of size, affecting sellers using platforms such as Amazon, eBay, Etsy, Poshmark, Mercari, and shipping tools like Pirate Ship, ShipStation, and Stamps.com.
