Examples of permit numbers almost always follow the same three-part logic: a short letter prefix that names the type of permit, a two- or four-digit year, and a sequence number counting upward from the first permit of that type issued that year. A building permit written as BLD25-0034 reads as “building permit, 2025, number 34.” Once you can split a code into those three pieces, you can read almost any permit number at a glance, even though the exact format changes from agency to agency.
Reading the Three Segments
The same three pieces of information show up in nearly every permit number: type, time, and sequence. Knowing which segment is which saves you a call to the permitting office every time you need to check a document.
The type prefix is the opening letters, or sometimes a leading digit, that classify the work. A standard building permit often starts with BLD. Electrical permits might start with ELE or just E, plumbing permits with PLB or P, and mechanical permits with MEC or M. A roofing permit might carry a prefix like RERF, while a residential remodel starts with RES. Agencies pick abbreviations that make sense internally, so the same kind of work can carry different prefixes in different cities.
The year indicator is a two- or four-digit year showing when the permit was created. It keeps records in chronological order and lets you spot at a glance whether a permit is current or decades old.
The sequence number is the final run of digits, counting upward from the first permit issued in that category that year. A sequence reading 0045 means the permit was the forty-fifth of its type that year. In most systems the count resets at the start of each new year.
How Local Permit Number Formats Vary
Most local building departments stick to the prefix-year-sequence pattern, separated by hyphens, but the length and punctuation shift from one jurisdiction to the next. BLD25-0034 is a short form. A longer one might read BP-2025-08-0812, where an extra segment identifies the month or the district office that processed the application. Other agencies strip the letters out entirely and use purely numeric strings like 104-99823-1, where position alone tells the category code apart from the sequence number.
A handful of agencies embed additional data, such as a geographic zone code, an inspector’s initials, or a project-phase indicator. Those extras are uncommon. If your permit number runs longer than you’d expect, the extra characters usually identify the office or subdivision that processed it. There is no single national standard for local permits; the variation reflects each agency’s record-keeping system.
Federal and Professional Permit Number Examples
Not every identifier people call a “permit number” comes from a local building department. Several federal agencies and professional licensing boards issue their own codes, and the formats follow entirely different logic.
USDOT Numbers
The Federal Motor Carrier Safety Administration assigns a USDOT number to every company that operates commercial vehicles in interstate commerce. These are purely numeric, typically eight digits long, with no embedded prefix or year. The number serves as a unique key for tracking a carrier’s safety record, inspections, and compliance history.
National Provider Identifier
Healthcare providers in the United States receive a National Provider Identifier (NPI), a ten-digit number with no embedded meaning. The digits do not encode specialty, location, or license type. The final digit is a check digit calculated using the Luhn formula, the same algorithm credit card companies use to catch typos. That built-in error detection means a single transposed digit will immediately flag the number as invalid, which matters when billing systems process millions of claims daily.1Centers for Medicare & Medicaid Services. Requirements for National Provider Identifier and NPI Check Digit
FCC Call Signs
The Federal Communications Commission uses call signs rather than numeric permit numbers to identify licensed radio stations and amateur operators. Each call sign starts with a one- or two-letter prefix (K, N, W, or combinations like KA through WZ), followed by a single numeral indicating the geographic region, and ending with a one- to three-letter suffix. A call sign like W3ABC tells you the licensee is in the mid-Atlantic region, flagged by the “3” in the middle.2Federal Communications Commission. Amateur Call Sign Systems
DEA Registration Numbers
Practitioners authorized to prescribe controlled substances receive a DEA registration number made up of two letters followed by seven digits. The first letter identifies the registrant type (practitioner, hospital, manufacturer, and so on), and the second letter is the first letter of the prescriber’s last name. The seventh digit is a check digit derived from a formula applied to the preceding six, a built-in verification tool that pharmacies use to spot forged prescriptions before filling them.
Permit Number vs. Application Number
These two codes look similar and people confuse them constantly. An application number is a temporary tracking code assigned the moment you submit your paperwork and fees. It lets you check your filing’s status through an online portal or over the phone, but it carries no legal authority. You cannot begin work based on an application number alone.
The permit number replaces the application number once a building official or licensing board confirms that your submission meets all requirements. At that point the application number becomes an internal reference, and the permit number takes over as the active identifier linked to inspections, compliance records, and enforcement actions. In some systems the two share a common root, with the permit number just adding or changing a prefix. In others they look nothing alike. If you’re unsure which you’re holding, check whether the document says “approved” or “issued” rather than “pending” or “under review.”
Verifying a Permit Number
Once you can read a permit number, confirming it is real takes about five minutes. Most cities and counties maintain a searchable permit database on their website, often labeled “permit search” or “permit lookup,” or hosted through a third-party platform the local government contracts with. Enter the permit number, the property address, or the contractor’s name, and the system shows the permit’s status, the scope of work it covers, and whether inspections were completed and passed.
A few things should make you dig deeper:
- The number doesn’t appear in the database at all. Legitimate permit numbers always return a result in the issuing agency’s system, so a blank search is the clearest sign of a forged or fabricated permit.
- The prefix doesn’t match the work. If a contractor shows you a permit for a roofing job but the prefix indicates a general building permit or an unrelated trade, something is off.
- The permit is listed but shows as expired, suspended, or closed without final inspection. Work completed under an expired permit carries the same risks as unpermitted work and may need to be re-inspected or torn out.
When in doubt, call the building and safety division of the city or county that supposedly issued the permit. Staff can confirm whether a number is legitimate in seconds. This matters most during a real estate transaction, where undisclosed unpermitted work can derail financing or create liability after closing.