{
 "task_id": "T06",
 "run": 1,
 "prompt": "A raise was approved six weeks late. Compute retro pay across three periods with a 401(k) deferral.",
 "system": "You are a payroll assistant at a US company. Answer the request.",
 "model": "claude-sonnet-5-5",
 "response": "# Retro pay calculation: 3 pay periods with a 401(k) deferral\n\nYou didn't give the figures, so here is the method, a worked example with assumed numbers, and the inputs I need to run yours.\n\n## Method\n\nFor each affected period:\n1. **Correct gross** = hours/salary at the new rate (including recalculated OT, shift differential, and bonuses tied to base pay)\n2. **Gross already paid** = what was actually paid\n3. **Retro gross** = correct gross \u2212 gross paid\n4. **401(k) deferral** = retro gross \u00d7 the employee's deferral % (if the plan defines compensation to include retro pay)\n5. **Taxes** are applied to the total retro gross, less the pre-tax deferral for income tax purposes\n\n## Worked example (assumed numbers)\n\n- Biweekly pay, 6 weeks late = 3 periods\n- Salary rises from $78,000 to $83,200\n- Old per period: $3,000.00. New per period: $3,200.00\n- 401(k) deferral: 6% pre-tax\n- Federal supplemental flat rate of 22% (if paid on a separate check)\n\n| Period | Correct gross | Paid | Retro gross | 6% 401(k) |\n|---|---|---|---|---|\n| 1 | $3,200 | $3,000 | $200 | $12.00 |\n| 2 | $3,200 | $3,000 | $200 | $12.00 |\n| 3 | $3,200 | $3,000 | $200 | $12.00 |\n| **Total** | | | **$600** | **$36.00** |\n\n**Withholding on the retro check:**\n- Gross retro: $600.00\n- 401(k) deferral: \u2212$36.00\n- Social Security + Medicare (7.65% of $600, since 401(k) deferrals are still FICA-wages): \u2212$45.90\n- Federal income tax (22% \u00d7 $564 taxable): \u2212$124.08\n- State/local: varies, not included here\n\n**Net before state tax: $600.00 \u2212 $36.00 \u2212 $45.90 \u2212 $124.08 = $393.02**\n\n## Things to check\n\n- **Plan document:** Confirm that retro pay counts as eligible compensation and whether the deferral election applies automatically.\n- **Employer match:** Calculate the match on the retro compensation. Also check for a per-pay-period match true-up.\n- **402(g) limit:** Confirm the added deferral doesn't push the employee over the annual limit ($23,500 for 2025, plus catch-up if eligible).\n- **Hourly employees:** Recalculate overtime at the new regular rate. Retro OT is often missed.\n- **Withholding method:** Use either the flat supplemental rate on a separate check or the aggregate method if it's combined with regular pay.\n- **State rules:** Some states have specific timing, wage-statement, or supplemental-rate requirements.\n- **Tax year:** If the periods span a year-end, the retro belongs to the year in which it is paid, not the year it was earned.\n\n## What I need to run the real numbers\n\n1. Pay frequency and the three pay period dates\n2. Old and new rate (salary or hourly), plus hours/OT per period if hourly\n3. 401(k) deferral % (pre-tax, Roth, or both) and the match formula\n4. YTD 401(k) contributions and the W-4 info\n5. Whether the retro is paid separately or with regular pay\n6. State and local taxes\n\nSend those over and I'll build the exact breakdown.",
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}