Imagine this scenario: You travel 500km to your exam center for the RRB NTPC CBT-2 (scheduled for Dec 20, 2025). You have your Admit Card, your original ID, and your pen. You reach the gate, put your thumb on the scanner, and… beep. Red light.
“Match Failed.”
The guard tells you to step aside. The clock is ticking. Your heart rate spikes.
This is not a horror story; this is a reality for hundreds of candidates every year. With the new strict Aadhaar-based biometric rules, a simple technical error can get you barred from the exam hall.
If you have “Mehendi” on your hands, sweaty palms, or a “Locked” Aadhaar, you are at risk. Here are the 3 critical steps to ensure you actually get to sit for the exam you studied for.
Step 1: The “Locked” Biometric Trap (Do This NOW)
Most students don’t even know they have this feature turned on.
UIDAI (the Aadhaar authority) allows you to “Lock” your biometrics to prevent fraud. It is a great security feature for your bank account, but it is a disaster for your exam. If your biometrics are locked in the UIDAI server, the RRB scanner at the exam center will reject your thumbprint instantly, and the center staff cannot fix it.
The Fix:
- Download the mAadhaar App or visit the UIDAI website.
- Login with your Aadhaar number + OTP.
- Check the “Biometric Lock” status.
- Unlock it at least 24 hours before your exam. (Servers can be slow; do not try to do this at the exam gate with poor signal).
Step 2: The “Sweaty Thumb” & Mehendi Syndrome
Winter exams like this December cycle are tricky. You might be wearing gloves, or you might be nervous-sweating. Cold or wet fingers distort the ridges of your fingerprint, causing a mismatch.
Also, a strict warning for female candidates: RRB guidelines specifically advise against applying Henna/Mehendi on your left thumb before the exam. The scanner cannot read through the dye.
Pro Tips for Exam Day:
- Carry a Handkerchief: Wipe your thumb vigorously right before you touch the scanner.
- The Forehead Trick: If the scanner fails twice, rub your thumb on your forehead. The natural oils on your skin actually help the scanner read ridges better than water or sanitizer does.
- Avoid Tattoos/Ink: Ensure your fingers are clean of any ink or deep cuts.
Step 3: “My Fingerprint Still Won’t Scan. What Now?”
If you have unlocked your Aadhaar and cleaned your hands, but the machine still fails (it happens!), do not let them send you home.
You have rights. The RRB guidelines have a protocol for “Biometric Mismatch.”
What to do:
- Don’t Panic: Politely but firmly tell the Center Supervisor: “Sir, my identity is genuine. Please use the Iris Scanner or the Face Authentication mode.”.
- The Undertaking Form: If electronic verification fails completely, you can request to sign a “Biometric Mismatch Undertaking”. This is a legal form where you declare you are the genuine candidate. They will take your photo and manual thumbprint and allow you to sit for the exam (subject to verification later).
- Show Alternative ID: Immediately present your backup Original Voter ID or 10th Marksheet to prove your identity matches the photo on the Admit Card.
Summary Checklist for Dec 20, 2025
- [ ] Check Aadhaar Lock Status: Unlock it today.
- [ ] Clean Hands: Remove Mehendi/Ink from your left thumb.
- [ ] Backup ID: Carry Original Voter ID/PAN Card just in case.
Don’t let a technical glitch ruin your year. Unlock that Aadhaar now and walk into that hall with confidence.
Watch this guide on the RRB NTPC exam Aadhaar unlock process to see exactly which buttons to press in the app.