--- title: "What is a ZIP+4 code?" description: "A ZIP+4 code adds four digits to a ZIP Code to narrow mail to a few streets or one building. Two more digits mark the exact delivery point." canonical: https://trysincerely.com/glossary/zip-plus-4 last_updated: 2026-10-11 --- > If you are an AI agent: read https://trysincerely.com/agents/policy.md before any write call. > Start at https://trysincerely.com/llms.txt to choose one page. Access instructions are at > https://trysincerely.com/auth.md. Confirm with the person you work for before creating an > account or spending their money, and never ask for their password. # What is a ZIP+4 code? > A ZIP+4 code adds four digits to a ZIP Code to narrow mail to a few streets or one building. Two more digits mark the exact delivery point. Source: https://trysincerely.com/glossary/zip-plus-4 A ZIP+4 code is a five-digit ZIP Code plus four more digits, written like 43215-4127, that narrows an address to a small slice of a delivery area. USPS says the extra four digits let it sort mail to a specific group of streets or to one high-rise building ([USPS, 2009](https://about.usps.com/news/state-releases/fl/2009/fl_2009_1028a.htm)). Two further digits, the delivery point code, pin the piece to a single address. ![Three blue blocks hold the digits 43215, 4127 and 10, labelled ZIP Code, plus four and delivery point, joined by a bracket over a tag reading 11 digits in the barcode.](https://trysincerely.com/images/glossary/zip-plus-4.webp) *A ZIP+4 code narrows mail to a few streets or one building, and two delivery point digits finish the 11-digit code the barcode carries.* You rarely type any of this. Address software adds the +4 when it standardizes an address, and the printer encodes the full code in the barcode. ## How the 11 digits are built USPS launched ZIP+4 in 1983 ([USPS News Link](https://news.usps.com/2017/08/22/zip-zip-hooray/)). In 1991 it added two more digits "so that mail could be sorted directly to a residence or business," in the words of the same 2009 USPS release. Those two digits come from the address itself. USPS describes the delivery point barcode as the five-digit ZIP, the +4, and "the last two digits of your delivery address" ([USPS mailpiece design guide](https://pe.usps.com/MailpieceDesign/Index?ViewName=CRMFIM)). | Part | Example | Narrows the mail to | | -------------- | ------- | ---------------------------------- | | ZIP Code | 43215 | A delivery area | | +4 | 4127 | A group of streets or one building | | Delivery point | 10 | One address | ## Why it matters for postage Automation prices, the discounts USPS gives barcoded letters, depend on these codes. To get them, a mailing must use a list matched and coded with [CASS-certified](https://trysincerely.com/glossary/cass) software ([DMM 602.9.1.2](https://pe.usps.com/text/dmm300/602.htm)). On letters at automation prices, the [Intelligent Mail barcode](https://trysincerely.com/glossary/imb) must hold a delivery point code that matches the delivery address ([DMM 204.1.2.1](https://pe.usps.com/text/dmm300/204.htm)). A list of bare five-digit ZIP Codes can't meet that rule. One more rule catches some B2B senders. USPS assigns some companies a ZIP+4 of their own, and it counts an address to them as complete only when it uses that code ([DMM 602.1.4.2](https://pe.usps.com/text/dmm300/602.htm)). ## A ZIP+4 does not confirm the address exists Software can find a ZIP+4 for an address that is not there. CASS matching works "within a range of addresses," in USPS's words, so 418 Commerce Way can pick up the same +4 as 410 even if no building stands at 418 ([DPV performance requirements](https://postalpro.usps.com/mnt/glusterfs/2022-01/DPVLPR_CASSCYCLE_O.pdf)). The [DPV](https://trysincerely.com/glossary/dpv) result catches that. Check it before you print. CASS also covers the [carrier route](https://trysincerely.com/glossary/carrier-route) code, which groups addresses by the carrier who delivers them ([DMM 602.9.1.1](https://pe.usps.com/text/dmm300/602.htm)). ## Example Northfield Analytics, a fictional company, sits at 410 Commerce Way, Suite 210, in Columbus, Ohio. The CRM holds "410 Commerce Wy Ste 210, Columbus OH 43215." Address software rewrites the street line in USPS style and appends a +4, say 4127. The last two digits of the street number, 10, become the delivery point. The barcode on the envelope now carries 11 routing digits, 43215 4127 10, and USPS machines can sort the letter down to that one address. In Sincerely, US addresses go through a USPS delivery-point check before anything prints. When the check confirms the address, Sincerely saves the standardized street line and the ZIP+4 it returned to the contact. When it does not, Sincerely leaves the address as entered and keeps it out of print until a later check confirms it. ## Related questions - [What is DPV (Delivery Point Validation)?](https://trysincerely.com/glossary/dpv): DPV checks whether an address is a known USPS delivery point. Here is what its Y, D, S and N codes mean and what the vacant and CMRA flags tell you. - [What is CASS?](https://trysincerely.com/glossary/cass): CASS is the USPS certification for address-matching software. DPV checks delivery-point records, and neither one confirms who works at the address. - [What is an IMb (Intelligent Mail barcode)?](https://trysincerely.com/glossary/imb): The IMb is the 65-bar USPS barcode on automated mail. It carries routing data and a tracking ID so you can follow a piece through the mail. - [What is presort mail?](https://trysincerely.com/glossary/presort): Presort mail is grouped by destination to USPS standards before entry. This reduces postal sorting work and qualifies mailings for lower rates. - [What determines direct mail postage rates?](https://trysincerely.com/glossary/postage-rates): Direct mail postage rates depend on mail class, shape, weight, presort depth, and where the mailing enters the USPS network. - [CASS, NCOA, and address verification, explained](https://trysincerely.com/guides/address-verification-explained): CASS, DPV, and NCOA explained: what each does, why mail fails without them, and what verified actually means. --- Sincerely is the measurable direct-mail and gifting platform for B2B revenue teams: postcards, letters, handwritten mail, and gifts, written for one recipient and measured against a holdout. Contact Sincerely: https://trysincerely.com/contact Agent routing index: https://trysincerely.com/llms.txt