Aadhaar Number Validator
Finance & Global IDsCheck an Aadhaar number's 12-digit format and Verhoeff checksum to catch typos. Runs in your browser; it can't confirm the number is registered with UIDAI.
Written by Anurag Rath · Reviewed by the thecalcu.com team · Last updated 16 October 2026
What is a Aadhaar?
The Aadhaar Number Validator checks whether a given 12-digit number follows the structural format mandated by the Unique Identification Authority of India (UIDAI). Aadhaar is India's national biometric identity system, every resident who has enrolled receives a unique 12-digit number linked to their fingerprints, iris scans, and demographic information.
The rules are straightforward: the number must be exactly 12 digits, the first digit must be between 2 and 9, and the last digit must match a Verhoeff checksum calculated from the others. Numbers are often written with spaces between each group of four digits (for example, 2345 6789 0123), but the underlying value is always 12 continuous digits. This validator accepts both spaced and unspaced entry.
It is important to understand what this validation does, and does not, confirm. A format and checksum check tells you that the number is structurally plausible, which is useful for catching typos before submitting a form. The checksum catches any single wrong digit and nearly all swapped neighbouring digits. It does not tell you whether the number is registered in UIDAI's database, whether it belongs to the person presenting it, or whether it is currently active. For any purpose requiring genuine authentication, use UIDAI's official APIs or the resident portal.
For Indian residents, Aadhaar is relevant across dozens of touchpoints: income tax e-filing (PAN–Aadhaar linking is mandatory), direct benefit transfers, pension scheme enrolment, and government portal logins. A typo in the 12-digit number causes application rejections and delays. Running a quick format check before submission prevents many of these avoidable errors.
You can use this tool alongside the PAN Number Validator when preparing documents that require both identifiers.
Why Use an Aadhaar Number Validator?
Government and financial forms that require Aadhaar often do not validate the format at the point of entry. A user who accidentally omits one digit or swaps two digits will only discover the error after submission, sometimes days later, via a rejection notice. This validator gives immediate feedback.
The most common data-entry errors are: entering 11 or 13 digits instead of 12, starting the number with a leading zero, including letters or special characters, and accidentally using a masked Aadhaar (which begins with "XXXX") in a field that requires the full number.
Developers building forms that collect Aadhaar numbers for KYC or government-linked services can also use the logic in this tool as a reference for client-side pre-validation before sending data to a backend.
Who Should Use This Validator?
Individuals completing government forms, Anyone filling KYC forms, linking PAN to Aadhaar, applying for subsidies, or enrolling in pension schemes needs to enter their Aadhaar correctly. A format check before submission is a simple safeguard against rejection.
Accountants and tax professionals, Chartered accountants and tax consultants who process Aadhaar–PAN linking or ITR filings for multiple clients can use this tool to verify each number before batch submission. Pair it with the PAN Number Validator and the Income Tax Calculator for a complete workflow.
HR and payroll teams, Companies collecting Aadhaar numbers from employees for PF enrolment, form 16 generation, or ESIC registration benefit from a quick format check during data collection to avoid rejected submissions downstream.
Developers and product teams, Engineers building onboarding flows, KYC modules, or government-integrated APIs need a simple client-side validation rule to reduce server-side errors and improve user experience.
NGOs and field workers, Organisations running beneficiary enrolment for government welfare programmes often collect Aadhaar numbers in the field. A mobile-accessible format checker helps catch errors before the form is finalised.
What Insights Does the Aadhaar Validator Give You?
The validator returns a clear pass or fail result alongside an explanation. On failure, it tells you specifically what is wrong, whether the number is too short, too long, contains non-digit characters, fails the checksum, or starts with 0 or 1. This is more useful than a generic "invalid" message when correcting data-entry errors.
On a successful format check, the tool confirms that the number is structurally plausible and reminds you that format validity does not equal authenticity. This scoping note matters in professional and legal contexts where the distinction between structural and database validation is important.
How to use this Aadhaar calculator
- Type or paste the Aadhaar number into the input field. You can enter it with spaces (e.g. 2345 6789 0124) or without (234567890124), both formats are accepted.
- The validator runs automatically as you type. You do not need to press a button.
- Check the Valid or Invalid badge below the input field.
- If the result is Invalid, read the error message to understand what needs correcting, for example, whether a digit is missing, a digit is mistyped (a checksum failure), or the number starts with 0 or 1.
- Once the badge shows Valid, the number is structurally correct and its checksum matches, so it's ready to use in forms that require Aadhaar.
- To validate a different number, clear the field and enter the new value.
Show formula & methodology ↓Hide formula & methodology ↑
Formula & Methodology
Rules checked, in order:
- Exactly 12 characters after removing spaces
- All characters are digits (0–9)
- The first digit is 2–9 (UIDAI doesn't issue numbers starting with 0 or 1)
- The Verhoeff checksum over all 12 digits comes out to zero. The 12th digit is the check digit for the first eleven.
The Verhoeff check: the algorithm walks the digits from right to left. For each digit it applies a fixed permutation that depends on its position (repeating every eight places), then combines the result with a running value using the multiplication table of the dihedral group D5. The number passes when the final value is 0. Unlike a simple sum, it detects every single-digit error and all swaps of adjacent digits.
Valid example: 2345 6789 0124, 12 digits, first digit 2, and the checksum comes to 0.
Invalid example (checksum): 2345 6789 0123, same digits with the last one changed, so the checksum fails.
Invalid example (first digit): 0234 5678 9012, fails because the first digit is 0.
Invalid example (length): 2345 6789 012, fails because only 11 digits are present.
A passing result still doesn't mean the number was issued to anyone. The checksum is public and any number can be built to satisfy it, so only UIDAI can confirm a number is real.
Authoritative references
- UIDAI: the issuing authority, with the official portal to check and retrieve your Aadhaar.
Related Tools
You may also find these useful: UPI ID Validator.