What is USPS CASS Certification?

Quick Definition

USPS CASS Certification (Coding Accuracy Support System) is an official validation that address verification software meets United States Postal Service standards for mail sorting accuracy and address standardization. CASS-certified systems must achieve at least 98.5% accuracy when validating addresses against USPS databases and provide standardized output required for presort mail discounts.

Understanding USPS CASS Certification

CASS Certification is the gold standard for address verification in the United States. Established by the USPS in 1991, CASS ensures that address processing software accurately matches addresses to the official USPS address database and formats them according to postal standards. This certification is not optional for businesses seeking presort mail discounts or processing high volumes of mail.

To achieve CASS certification, software vendors must submit their systems to rigorous testing by the USPS. The testing process evaluates accuracy against a sample database of addresses, checking that the software correctly identifies deliverable addresses, adds ZIP+4 codes, assigns carrier route information, and standardizes address formatting. Systems must maintain 98.5% accuracy or higher to pass certification, and this certification must be renewed annually.

CASS-certified software provides critical data elements beyond basic address validation. It returns ZIP+4 codes that specify delivery areas down to a city block or building, carrier route codes that identify the specific mail delivery route, delivery point barcodes for automated sorting, and DPV (Delivery Point Validation) codes that confirm whether an address is deliverable. This enriched data enables the USPS to sort mail more efficiently and allows businesses to qualify for presort discounts of up to 40% on postage.

For businesses, using CASS-certified address verification is essential for several reasons. First, it dramatically reduces undeliverable mail - studies show CASS certification reduces mail returns by 80-85%. Second, it qualifies mailings for significant postage discounts through presort programs. Third, it ensures compliance with USPS regulations for bulk mailing. Fourth, it improves overall data quality by maintaining clean, standardized customer addresses.

The financial impact of CASS certification is substantial. A company mailing 100,000 pieces monthly at standard postage ($0.63 per piece) spends $63,000. With CASS-certified addressing and presort discounts, costs can drop to $0.40-0.45 per piece, saving $18,000-23,000 monthly. Additionally, eliminating returned mail saves on reshipping costs, customer service time, and lost sales opportunities. For high-volume mailers, CASS certification typically pays for itself within weeks.

How CASS Certification Works

Vendor Application: Software provider applies to USPS for CASS certification and receives test database
System Testing: Provider processes test addresses through their verification system, generating standardized output
Accuracy Evaluation: USPS evaluates results against known correct values, measuring accuracy across multiple criteria
Certification Issuance: If system achieves 98.5% accuracy or higher, USPS grants CASS certification with unique ID number
Database Updates: Certified provider receives monthly USPS database updates to maintain current address data
Annual Renewal: Certification must be renewed yearly through retesting to ensure continued compliance and accuracy

Key Benefits of CASS Certification

Postage Discounts

Qualify for USPS presort discounts up to 40% on bulk mailings with CASS-certified addressing

Reduce Undeliverable Mail

Decrease mail returns by 80-85% through accurate address verification and standardization

USPS Compliance

Meet postal regulations and requirements for bulk mailing and presort operations

Faster Delivery

Improve mail delivery speed through accurate sorting codes and carrier route information

Data Quality

Maintain clean, standardized customer address database with official USPS formatting

Cost Savings

Save thousands monthly on postage, reshipping, and returned mail processing costs

Common Use Cases

1. Direct Mail Marketing

Process marketing mailings with CASS-certified addresses to qualify for presort discounts and ensure maximum delivery rates

2. E-commerce Shipping

Verify customer shipping addresses with CASS certification to reduce failed deliveries and improve customer satisfaction

3. Billing & Statements

Ensure bills and financial statements reach customers reliably by using CASS-verified addresses for mailings

4. Magazine & Subscription Services

Maintain accurate subscriber addresses and qualify for periodical mailing discounts through CASS certification

5. CRM Database Cleansing

Clean and standardize customer databases using CASS-certified verification to improve data quality and deliverability

CASS Certification vs Standard Address Validation

Feature	Standard Validation	CASS Certified
USPS Certification	No official certification	Officially certified by USPS
Accuracy Requirement	Variable (typically 90-95%)	Minimum 98.5% accuracy
Database Updates	Irregular or quarterly	Monthly USPS updates required
ZIP+4 Codes	Often not provided	Always provided when available
Carrier Route	Not included	Full carrier route codes
Presort Eligibility	Not eligible for discounts	Qualifies for presort discounts
Cost	Lower	Higher, but offset by savings
Best For	Basic address checking	Bulk mailing, compliance, savings

How to Implement CASS-Certified Verification with Sthan.io

Sthan.io is USPS CASS-certified and provides all required data for presort discounts. Here's how to implement it:

Step 1: Get API Credentials

Step 2: Make API Request

POST https://api.sthan.io/v1/verify/address
Content-Type: application/json
Authorization: Bearer YOUR_API_KEY

{
  "street": "1600 Amphitheatre Parkway",
  "city": "Mountain View",
  "state": "CA",
  "zipCode": "94043"
}

Step 3: Handle CASS-Certified Response

{
  "status": "verified",
  "confidence": 100,
  "standardizedAddress": {
    "street": "1600 AMPHITHEATRE PKWY",
    "city": "MOUNTAIN VIEW",
    "state": "CA",
    "zipCode": "94043-1351"
  },
  "cassData": {
    "dpvConfirmation": "Y",
    "carrierRoute": "C909",
    "deliveryPoint": "00",
    "checkDigit": "2",
    "recordType": "S"
  },
  "certification": {
    "cassCertified": true,
    "cassNumber": "CASS-123456",
    "processDate": "2025-12-03"
  }
}

Frequently Asked Questions

CASS certification ensures address verification software meets USPS accuracy standards, which is required for presort mail discounts, reduces undeliverable mail by up to 85%, and ensures compliance with postal regulations for bulk mailing operations.

CASS certification must be renewed annually. Software providers must retest their systems against current USPS databases and maintain 98.5% accuracy to retain certification. USPS updates address databases monthly, requiring regular system updates.

CASS-certified systems provide standardized addresses, ZIP+4 codes, carrier route codes, delivery point barcodes, and DPV (Delivery Point Validation) confirmation. This data enables presort discounts and improves mail delivery success rates.

You need CASS-certified address verification if you send bulk mail (more than 500 pieces), want presort postage discounts, need to maintain high delivery rates, or must comply with postal regulations. E-commerce and marketing companies benefit significantly from CASS certification.

Related Terms

Address Verification

Address Standardization

ZIP+4 Code

Address Validation

Address Parsing

REST API

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