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Case Study #168 — 300 Software Failure Case Studies

Denmark tax debt-collection system failure

Denmark's automated tax debt-collection system (EFI) failed to collect the vast majority of outstanding tax debts it was built to recover and had to be scrapped, at a cost estimated in the hundreds of millions of dollars and years of lost tax revenue.

2013-2015
When it happened
Government
Sector
#168 of 300
Ranked by documented impact
01 — What Happened

The damage was public. The root cause was preventable.

Denmark's automated tax debt-collection system (EFI) failed to collect the vast majority of outstanding tax debts it was built to recover and had to be scrapped, at a cost estimated in the hundreds of millions of dollars and years of lost tax revenue.

Government
Sector affected
2013-2015
Date of the event
#168
Rank in the 300 Software Failure Case Studies
2
Distinct root-cause clauses identified below
02 — The Root Cause

What the software actually got wrong

The debt-collection software could not correctly calculate which debts were still legally collectable, incorrectly writing off or mishandling large volumes of debt, and repeated attempts to patch the system failed to bring it up to a workable standard.

01Root Cause

The debt-collection software could not correctly calculate which debts...

What Happened

The debt-collection software could not correctly calculate which debts were still legally collectable, incorrectly writing off or mishandling large volumes of debt

How Requs AI Catches This

Requs AI Edge Case flags this exact pattern at the requirements and architecture stage — before a single line of code implementing it exists — so the assumption behind it gets challenged while it is still cheap to fix.

02Root Cause

Repeated attempts to patch the system failed to bring...

What Happened

repeated attempts to patch the system failed to bring it up to a workable standard

How Requs AI Catches This

Requs AI Software FMEA traces this failure mode back to the system-level hazard it feeds, tagging it against the Common Defect Enumeration so it surfaces in review instead of in the field.

03 — How This Gets Caught Before It Happens

Beyond code coverage and "shall" testing

Root causes like this one rarely show up in code coverage or requirements-compliance testing, because nobody wrote a requirement anticipating the specific edge case that broke. Requs AI Edge Case and Requs AI Software FMEA are built to surface exactly this class of overlooked failure mode — before the software is written.

Requs AI Edge Case

Surfaces this before code exists

Identifies edge cases like this one at requirements and architecture time, using the Common Defect Enumeration to catalog failure patterns seen across hundreds of real-world software failures — including this one.

Requs AI Software FMEA

Connects the failure mode to the hazard

Traces this class of root cause directly to the system-level hazard it can produce, so a defect pattern like this one gets flagged during design review instead of after it ships.

Find the overlooked root causes before they ship.

Schedule a demonstration, or explore how Requs AI Edge Case and Software FMEA use the Common Defect Enumeration.