010-0000-1234? The Self-Issue Number Mistake That Costs One Zero
What goes wrong when 010-0000-1234 is submitted instead of 010-000-1234 — prevention logic and how to reissue correctly.
The Most Common Self-Issue Mistake
Self-issuing a cash receipt to the NTS-designated number is an important procedure used when a customer's identity is unavailable. And there's one mistake that comes up more than any other: getting the digit count wrong on the self-issue number.
One Extra Zero in the Middle
The error is almost always the same — one too many zeros in the middle segment:
| Number Format | Digits | Notes | |
|---|---|---|---|
| Correct (NTS-designated) | 010-000-1234 | 10 digits | Official self-issue number |
| Wrong (common mistake) | 010-0000-1234 | 11 digits | Standard mobile number format |
The NTS self-issue number is 10 digits — unlike a standard Korean mobile number (11 digits). Developers often muscle-memory the 11-digit format and end up submitting 010-0000-1234 without noticing.
What Happens When You Submit the Wrong Number
If your system sends an issuance request with 010-0000-1234 (11 digits), here's what can go wrong:
- Misrouted issuance: The receipt doesn't go to the self-issue pool — it's issued as an income deduction receipt instead. Once that happens, it cannot be converted back to self-issue. This can constitute a violation of the mandatory cash receipt issuance obligation for the merchant.
Prevention and Recovery — Steps for Developers
Step 1: Strengthen input validation
In your self-issue logic, add a regex check to reject 11-digit inputs. If the number starts with 010000, either auto-correct to 0100001234 or block the submission outright.
Step 2: Use a constant for the self-issue number
When running in "self-issue" mode (no customer identity available), define the correct number as a constant in your codebase rather than accepting it as a runtime input.
Step 3: If a wrong issuance already occurred
If a request was sent with 010-0000-1234, immediately locate the original transaction number, cancel the receipt, then reissue using the correct number 010-000-1234.
Why This Matters
Self-issue is the mechanism that prevents gaps in tax reporting. One wrong digit degrades the integrity of your entire settlement dataset — and can expose the merchant to penalties.
When integrating with the Hecto Financial API, digit validation for the identity field must be included in your shared validation module without exception.
Need technical support?
Code Samples
HectoFinancial GitHub