ARQC Error 05 – "Do Not Honour" Decline – The Complete Fix Details (2026)

[Student]

What "Error 05" Actually Means In EMV transactions, response code 05 = "Do Not Honour" – the issuer refuses to authorize the transaction. It's the most common decline when testing/writing cards – not a card problem, but an issuer rejection.

Real 2025 stats (from my 4 842 card tests):

• Error 05 on 68.4 % of failed online auth attempts
• Fixed with correct method: 94 %+ success on retry/new card

Why You Get Error 05 on ARQC Transactions (Top Causes 2025)​

#	Cause	Why It Triggers 05	Fix Success Rate
1	Fake/Static ARQC	Issuer validates real ARQC – fake fails	0 % (can't fix fake)
2	Wrong Session Key / No Real Keys	ARQC doesn't match issuer calculation	0 % without real keys
3	Velocity / Risk Flags	Too many attempts, unusual amount/IP	88 % (wait + new IP)
4	Incorrect Data Block	CDOL1 wrong (amount, UN, terminal data)	92 % (correct CDOL)
5	ATC Mismatch	Card ATC not sequential	96 % (reset ATC)
6	Terminal Not Certified	Merchant ID blacklisted	85 % (use legit merchant)

Detailed Fixes for Each Cause (What Actually Works 2025)​

Cause 1 & 2 – Fake ARQC / No Real Keys (Most Common – Can't Fix)

• Public generators (X2, BP-Tools fake) → static ARQC → issuer rejects.
• Only real fix: Real issuer master keys (from logs/insider) → generate valid ARQC.
• Success: 0 % with fake ARQC online.

Cause 3 – Velocity / Risk Flags (88 % Fixable)

• Too many attempts → bank flags card.
• Fix:
  1. Wait 24–72 hours.
  2. New IP (Decodo residential).
  3. Lower amount first ($100–$500).
  4. Different merchant.

Cause 4 – Incorrect Data Block (92 % Fixable)

• Wrong CDOL1 → ARQC doesn't match.
• Fix: Use exact terminal data from real transaction trace.

Cause 5 – ATC Mismatch (96 % Fixable)

• ATC not sequential → issuer rejects.
• Fix: Reset ATC to 0001 or match last known.

Cause 6 – Terminal Blacklisted (85 % Fixable)

• Merchant ID flagged.
• Fix: Use different site/gateway.

Real Example Fix from Last Week (Error 05 → Success)​

• Card: JCOP with fake ARQC → Error 05 on $5k hit
• Wait 48 h + new Decodo IP + lower to $1k → approved
• Then max hit $42k → success

Bottom Line – December 2025​

Error 05 = issuer "Do Not Honour" – usually fake ARQC or risk flag. Can't fix fake ARQC online – need real keys. Velocity/IP fixes work 88 %+ of time.

Real money avoids online ARQC entirely (gift cards, aged accounts).

Want my full ARQC pack? DM for “ARQC Error Fix Pack December 2025”:

• Real vs fake ARQC examples
• Velocity reset guide
• Terminal whitelist

Or accept Error 05 and move to real methods.

Your choice.