UoP Salary Calculator — Project Skill

Verified Calibration Data (Serhii, 27 000 zł brutto, 2025)

Real net payments from mBank statement:

Serhii's parameters:

• Brutto: 27 000 zł/mc, no PPK
• KUP: reverse-engineered = 11 215,88 zł/mc for full months
• Fixed deductions: Medicover 15,75 + Multisport 167,82 = 183,57 zł/mc
• Work days 2025: [23,20,21,22,22,21,23,21,22,23,20,23]

Model accuracy: ~1.2% annual error. Jan/Feb/Apr/May: exact (0–4 zł diff).

Tax Formulas (Confirmed Correct)

ZUS_social  = brutto × (9.76% + 1.50% + 2.45%)   ← capped by 30x limit (em+re only)
ZUS_health  = (brutto − ZUS_social) × 9%
KUP         = 50% × honorarium_fraction × (brutto − ZUS_social) × (work_days/total_days)
              ← capped at 120 000 zł/year; after cap: KUP = 250 zł/mc flat
taxbase     = max(0, brutto − ZUS_social − KUP)
tax         = max(0, taxbase × 12% − 300)   [cumulative dochód ≤ 120 000 zł]
              OR taxbase × 32%              [above threshold]
              OR split at crossing month
netto       = brutto − ZUS_social − ZUS_health − tax − PPK_employee − fixed_deductions

ZUS rates (unchanged since 2014, safe to hardcode): em 9.76%, re 1.5%, ch 2.45%, zdrow 9%. Tax brackets (safe to hardcode): 12% / 32% threshold 120 000 zł, kwota wolna = 300 zł/mc reduction.

ZUS 30x Cap by Year

Formula: 30 × prognozowane przeciętne wynagrodzenie miesięczne (set annually by Minister). Cap applies only to em+re. Chorobowa (2.45%) has NO cap. Zdrowotna base shifts when ZUS_social drops.

Critical KUP Facts (Research-Confirmed)

What "80% KUP" actually means (common expat misconception):

• "80% KUP" does NOT exist as a tax rate in Polish law
• Only two rates: 50% (honorarium autorskie) and 20% (some civil contracts)
• "80%" = the fraction of salary/time classified as honorarium autorskie
• Actual KUP = 50% × 80% × base = 40% of base — not 80%

Who controls KUP — IMPORTANT:

• The honorarium autorskie provision MUST be in the employment contract or an annex
• BUT the employee does not calculate it — HR/payroll does everything
• The employee only reports creative hours (e.g. 7h/8h via timesheet)
• The employer's payroll system derives the KUP PLN amount from that
• Users typically don't know the exact PLN unless they look at their pasek płac

KUP UX — three input modes:

1. None — no koszty autorskie; standard 250 zł/mc flat (explain: this is the default fallback, minimal benefit)
2. Auto-estimate — user picks % of time that's twórcze → calculator derives KUP via legal formula
3. Manual from payslip — user enters exact PLN from "koszty uzyskania przychodu" line on pasek płac (most accurate)

Important constraint: Ulga dla młodych (PIT-0, under 26) and 50% KUP cannot be used simultaneously.

Known Anomalies (Do NOT Model — Employer-Side Only)

→ Show November/December with * marker explaining they will be higher in reality. → Annual total is more reliable than individual months for Q4.

Polish Public Holidays (Verified — Mon-Fri weekday occurrences per month)

Computed from full statutory list: Nowy Rok, Trzech Króli, Wielkanoc, Poniedziałek Wielkanocny, Święto Pracy, Święto Konstytucji, Zesłanie Ducha Świętego (Sunday, never weekday), Boże Ciało, Wniebowzięcie NMP, Wszystkich Świętych, Święto Niepodległości, Boże Narodzenie ×2.

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