Since February 2016, Amazon has been requiring sellers to provide valid tracking numbers for at least 95% of your shipments. Sellers will not need to provide tracking for freight shipments, or for items shipped in Standard Mail or First Class Mail envelopes (e.g. screen protectors, greeting cards).
USPS mail shipped via First Class Letter, Large Envelope and First Class Flat don't have tracking number since they are not supposed to contain merchandise, and have no realistic tracking. Therefore Circle.us won’t be able to upload the tracking number to your marketplace automatically after you print the label. If you wish to have tracking service for your shipment, please select other package types.
Should you have any questions on the non-trackable shipments, please do not hesitate to contact us.