Debts Averaged Out of Thin Air — Python Bug Hunt

Briefing

Modelled on Robodebt, the Australian government's automated welfare debt-recovery scheme (2016–2019): it averaged a person's annual income from tax records evenly across the year's fortnights and compared that average with the income they had reported fortnight by fortnight. Anyone whose earnings were uneven — casual or seasonal work — could be issued a debt they did not owe. In 2019 the Federal Court found a debt based on averaging unlawful, and a Royal Commission reported on the scheme in 2023.

This project is a reconstruction. assess.py computes a debt by spreading the annual figure across 26 fortnights.

Fix assess so each fortnight is judged on that fortnight's own income, and a mismatch with the annual figure is flagged for review — never turned into a debt.

Bug report

BUG-OCI · Priority: Critical · Reported by: ombudsman referral

assess(annual_income, fortnights) — each fortnight is {"reported": int, "actual": int or None, "paid": int}.

• the income for a fortnight is "actual" (payslip evidence) when it is not None, otherwise the "reported" figure; the annual figure is NEVER divided across fortnights
• debt = sum over fortnights of max(0, paid - rules.entitlement(income))
• review = abs(annual_income - sum of the incomes used) > rules.REVIEW_TOLERANCE

Returns {"debt": int, "review": bool}.

Observed: a casual worker who earned everything in half the year and claimed benefits correctly in the other half was issued a debt of 4550.

Logs

[oci] client 88231 annual=26000 averaged=1000/fn
[oci] client 88231 raised debt=4550 (13 fortnights over-paid)

The code as shipped

src/compliance/assess.py (editable)

rules = bug_require("./rules.py")


def assess(annual_income, fortnights):
    fortnightly = annual_income // rules.FORTNIGHTS_PER_YEAR
    debt = 0
    for f in fortnights:
        owed = f["paid"] - rules.entitlement(fortnightly)
        if owed > 0:
            debt += owed
    used_total = fortnightly * len(fortnights)
    review = abs(annual_income - used_total) > rules.REVIEW_TOLERANCE
    return {"debt": debt, "review": review}

Read-only context: src/compliance/rules.py.