Certain direct mail campaings may benefit from a process known a Density and Sequence Coding.

Density and Sequence Coding in Direct Mail: How It Works and           Why It Matters

Certain direct mail campaigns can benefit significantly from a process known as Density and Sequence Coding.

USPS Marketing Mail (formerly Standard Mail or “Bulk Mail”)

These terms all refer to essentially the same category of mail. When mailpieces are entered into the USPS system, they are organized and grouped by sequence and geography before reaching the local post office. This reduces the amount of sorting the USPS must perform.

Following this same concept, all addresses are matched against the USPS database for validation and certification. However, there is far more data associated with an address than just street, city, state, and ZIP code.

Some USPS-certified mailers can access this additional data, match it to your mailing list, and append key fields that further improve presorting and qualification for deeper postage discounts.

In some cases, this can reclassify the mailing into lower-cost secondary rate categories. By appending data such as carrier route and walk sequence, mailings can qualify for better pricing on larger neighborhood-based lists. It can also allow a piece to mail as a flat rather than a letter, eliminating the need for folding or adding multiple tabs.

Why Route and Sequence Data Matters

Appending carrier route and walk sequence data to a mailing list allows mailers to qualify for the deepest USPS Marketing Mail and Periodicals postage discounts—specifically High Density and Saturation rates.

These rates are significantly lower than basic presorted or automation rates because the mail is already sorted in the exact order the carrier delivers it. This saves the USPS substantial processing time, and those savings are passed on to the mailer.

How It Works

To perform density and sequence coding, several components are required:

1. Access to the USPS database
   The USPS address database is live and updates every 2–3 hours, 24/7. A secure connection is required.

2. Certified address-matching software
   Specialized software matches your mailing list to the official USPS database.

3. Data analysis and appending
   Once matched, additional USPS fields—such as carrier route, delivery point, and walk sequence—are appended to each record in your list.

Walk Sequence Data

The USPS provides data products such as the Delivery Sequence File (DSF2) to licensed partners and vendors. This data sorts addresses into the precise order a carrier walks their route and assigns a unique sequence number to each address.

Preparation Requirements

• Mailers must use CASS-certified software to ensure address accuracy.

• Walk sequence data must be updated within 90 days of the mailing date.

• Mailpieces must be physically sorted into trays or bundles in walk-sequence order and properly labeled.

Eligibility and Requirements

To qualify for enhanced carrier route pricing, mailings must meet the following criteria:

Volume

• Minimum of 200 pieces or 50 pounds per mailing.

Density

High Density

• At least 125 pieces per carrier route, or

• One piece for every possible delivery if the route has fewer than 125 stops.

Saturation

• At least 90% of active residential addresses, or

• 75% of total active possible delivery addresses on each carrier route.

Automation Compatibility

For letter-size mail at high-density or saturation rates:

• Pieces must be automation-compatible and include a Delivery Point Barcode (DPBC).

• An exception applies to simplified-address mail using ECRWSS (Enhanced Carrier Route Walk Sequence Saturation), which does not require a DPBC.

Benefits

Meeting these requirements can result in substantial postage savings:

• Up to $0.05 per letter

• Up to $0.15 per flat

This method is especially beneficial for:

• Realtors - GeoFarming

• Local businesses

• Real estate and retail advertisers with dense local coverage

• Newspapers

• Political campaigns

Most mailers implement this process using specialized software or professional mailing services. Additional technical requirements can be found in the USPS Domestic Mail Manual (DMM).

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If you have a specific mailing list size or mailpiece type (letter or flat) in mind, we can estimate potential savings and determine whether this process is a good fit for your campaign.

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