Understanding USPS Returned Mail Codes

USPS returned mail codes are specific codes used by the United States Postal Service (USPS) to categorize and explain the reasons why mail cannot be delivered as addressed.

3 minute read

What is a USPS Returned Mail Code?

USPS returned mail codes are specific codes used by the United States Postal Service (USPS) to categorize and explain the reasons why mail cannot be delivered as addressed. These codes are printed on or attached to the mailpiece and serve as crucial feedback for businesses and individuals about the deliverability of their mail. Understanding these codes is essential for organizations, especially medium-to-large businesses, as they often rely on direct mail for marketing or need to send important documents to their customers.

Common and Relevant USPS Returned Mail Codes for Businesses

For businesses that engage in direct-mail based marketing or require reliable document delivery, some USPS returned mail codes are particularly pertinent:

Nixie Codes (Reasons for non-delivery)

UAA (Undeliverable as Addressed): This is one of the most common reasons for mail returns. It indicates that the address is incorrect, incomplete, or outdated.
IA (Insufficient Address): This code is used when essential parts of the address are missing or incomplete.
NSN (No Such Number): This code indicates that the address number does not exist on the street or is not valid.
ANK (Addressee Not Known): Used when the addressee is unknown at the address provided.
UTF (Unable to Forward): This code is applied when mail cannot be forwarded to the new address, often because forwarding instructions have expired or are not provided.

Temporary Return Codes

ATA (Attempted Not Known): Indicates an attempt to deliver was made, but the recipient is not known at the address.
DEC (Deceased): Used when the recipient is deceased, a particularly important code for financial institutions or legal services.

Refusal and Rejection Codes

REF (Refused): This mail was refused by the recipient at the address and is being returned to the sender.
NMR (No Mail Receptacle): Indicates that there is no receptacle to receive mail at the provided address.

The Importance of Reducing Returned Mail

Reducing the volume of returned mail is crucial for businesses for several reasons:

Cost Efficiency: Returned mail represents a direct cost in terms of wasted materials and postage, not to mention the potential lost opportunity for sales and communications.

Customer Relationships: Accurate delivery of marketing materials and important documents is vital for maintaining trust and reliability with customers.
Operational Efficiency: High volumes of returned mail can lead to significant administrative burdens, requiring additional staff time to manage and resolve address issues.

CASS-Certified Address Verification Solutions

To combat issues related to returned mail, businesses can utilize CASS (Coding Accuracy Support System)-certified software. Firstlogic offers such a solution, designed to help businesses verify addresses before mailings. This software ensures that addresses are complete, accurate, and conform to USPS formatting guidelines, significantly reducing the likelihood of mail returns.

Firstlogic’s software is unique in that it provides bulk, high-volume, and unlimited usage address verification without licensing based on usage. This feature is particularly beneficial for medium-to-large enterprises that process large quantities of mail, allowing them to maintain consistent operational costs regardless of the volume of addresses verified.


Understanding and managing USPS returned mail codes effectively is a crucial part of business operations for companies relying on direct mail strategies. Utilizing advanced CASS-certified software like that offered by Firstlogic can help ensure that mail reaches its intended recipients, reducing costs and enhancing customer engagement.