By the RxReflex Content Team · Last reviewed August 6, 2026
A DEA number is two letters followed by seven digits. The first letter is the registrant type, the second letter is the first letter of the prescriber's last name, and the seventh digit is a check digit you can verify with three quick sums. Federal Requirements is 18.75% of the 2026 PTCE — up from 12.5%, the biggest change on the new outline.
Two letters, then seven digits — for example AB1234563. Each piece carries information:
| Position | What it means |
|---|---|
| 1st letter | Registrant type (see the table below) |
| 2nd letter | The first letter of the prescriber's last name — or the digit 9 for a business |
| Digits 1–6 | The registrant's assigned number |
| 7th digit | The check digit — mathematically derived from the first six |
| Letter | Registrant type |
|---|---|
| A · B · F | Practitioner, hospital, clinic, or pharmacy |
| M | Mid-level practitioner — NP, PA, CRNA, CNS, nurse-midwife, optometrist |
| X | Retired in 2023. Formerly the buprenorphine (MAT) waiver prefix |
The X change is current-events material and a fair 2026 exam target. The separate DATA-waiver registration was eliminated, so a practitioner no longer needs an X number to prescribe buprenorphine for opioid use disorder. If a study resource still teaches the X-waiver as a live requirement, it predates the change.
A prescription from a nurse practitioner with an M DEA number is normal and valid — mid-level practitioners may prescribe controlled substances where state law authorizes it. Rejecting it as invalid is a wrong answer.
The second letter must match the first letter of the prescriber's last name. This is the fastest check on the page and it needs no math.
If a controlled-substance prescription from Dr. Sarah Lopez carries the DEA number AS1234563, the second letter is S but the last name starts with L. The number fails before you calculate anything — flag it to the pharmacist.
A name change is the honest exception: a prescriber who marries or otherwise changes their last name keeps the old DEA number until it is updated. That is why a mismatch means escalate to the pharmacist, not "refuse the prescription."
Using AB1234563 — the digits are 1 2 3 4 5 6 3:
| Step | Do this | Result |
|---|---|---|
| 1 | Add the 1st + 3rd + 5th digits | 1 + 3 + 5 = 9 |
| 2 | Add the 2nd + 4th + 6th digits, then × 2 | 2 + 4 + 6 = 12 → × 2 = 24 |
| 3 | Add steps 1 and 2. The last digit of that total must equal the 7th digit | 9 + 24 = 33 → 3 = 3 ✓ valid |
That is the whole algorithm. It takes about ten seconds once you've done it three times, and it is one of the few places on this exam where a mechanical procedure gives you a definite right answer.
Passing the math does not mean the number is real. The check digit only proves the number is well-formed — a fabricated number can be built to pass it. Active registration status is verified with the DEA, not with arithmetic.
| Form | Used for | The detail that gets tested |
|---|---|---|
| DEA Form 222 / CSOS | Ordering Schedule II controlled substances | C-IIs cannot go through the regular wholesaler system. Paper Form 222 or electronic CSOS, signed by the registrant or an authorized power of attorney. Schedules III–V use normal ordering. |
| DEA Form 41 | Documented destruction of controlled substances | Covers expired, surplus, spilled, or broken stock. Most pharmacies use a reverse distributor; some self-destruction is allowed with witnessing requirements. |
| DEA Form 106 | Reporting theft or significant loss | Filed within one business day of discovery, plus notification to local law enforcement and the state board as required. |
| DEA Form 224 | Initial pharmacy registration | 224a is the renewal. Registration is what makes the pharmacy a DEA registrant in the first place. |
A count discrepancy is not automatically a Form 106. The sequence is: tell the pharmacist, recount, investigate — and only if a significant loss is confirmed does the 106 get filed. Exam questions often stop at the recount.
Add the 1st, 3rd, and 5th digits. Add the 2nd, 4th, and 6th digits and multiply that sum by two. Add the two results — the last digit of the total must equal the 7th digit of the DEA number. Also confirm the second letter matches the prescriber's last-name initial.
It identifies the registrant type. A, B, and F indicate a practitioner, hospital, clinic, or pharmacy. M indicates a mid-level practitioner such as a nurse practitioner or physician assistant. X was retired in 2023.
No. The X prefix marked the old buprenorphine (DATA) waiver, and that separate registration was eliminated in 2023. A practitioner no longer needs an X number to prescribe buprenorphine for opioid use disorder.
Ordering Schedule II controlled substances. C-IIs cannot be ordered through the regular electronic wholesaler system — they require a paper Form 222 or the electronic CSOS, signed by the registrant or an authorized power of attorney. Schedules III through V use normal ordering.
Form 41 documents intentional, witnessed destruction of controlled substances. Form 106 reports theft or significant loss, and is filed within one business day of discovery.
No. It only proves the number is correctly formed. A fabricated number can be constructed to pass the math. Active registration status has to be verified with the DEA.
Federal Requirements jumped to 18.75% of the 2026 exam. RxReflex's DEA Number Check cheat sheet is free in the app, and the Learn path drills the federal rules as scenario questions with a rationale for every option. Free to start on iOS and Android.
What Changed on the 2026 PTCB ExamNew domain weights, what was removed, and how to adjust your study plan.
Controlled Substance SchedulesC-II to C-V rules, refill limits, and DEA forms — the law block that grew most in 2026.
How to Read a PrescriptionThe anatomy of an Rx, all ten DAW codes, and how to read an NDC off a stock bottle.Prefer a printable version? Grab “The PTCB Pass Code” free PDF — the highest-yield facts, formulas & traps on 22 pages.
Last reviewed August 6, 2026 by the RxReflex Content Team. Educational use only — not medical advice. Exam policies and fees are set by PTCB — always confirm details at ptcb.org. Verify clinical specifics with your pharmacist or a current label source such as DailyMed. RxReflex is not affiliated with or endorsed by the Pharmacy Technician Certification Board (PTCB).