{
 "task_id": "T06",
 "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-opus-5-5",
 "response": "# Retro Pay Calculation: Raise Approved 6 Weeks Late\n\nYou didn't include the employee's figures, so this example uses the assumptions below. Send me the actual numbers and I'll rerun it.\n\n## Assumptions\n\n| Item | Value |\n|---|---|\n| Pay frequency | Biweekly (26/yr), so 6 weeks = 3 periods |\n| Old salary | $65,000 |\n| New salary | $70,000 |\n| Effective date | Start of Period 1 (full periods) |\n| 401(k) pre-tax deferral | 6% of eligible comp |\n| Employer match | 100% up to 4% |\n| Federal withholding | 22% flat supplemental rate (retro paid as a separately identified payment) |\n| State/local | Excluded (varies by state) |\n\n## Step 1: Per-Period Difference\n\n- Old biweekly: $65,000 \u00f7 26 = **$2,500.00**\n- New biweekly: $70,000 \u00f7 26 = **$2,692.31**\n- Difference per period: **$192.31**\n\n## Step 2: Retro by Period\n\n| Period | Old Gross | New Gross | Retro Owed |\n|---|---|---|---|\n| 1 | $2,500.00 | $2,692.31 | $192.31 |\n| 2 | $2,500.00 | $2,692.31 | $192.31 |\n| 3 | $2,500.00 | $2,692.31 | $192.31 |\n| **Total** | | | **$576.92** |\n\n*Total computed as $5,000 \u00d7 3/26 = $576.92 to avoid rounding drift ($192.31 \u00d7 3 = $576.93).*\n\n## Step 3: 401(k) Deferral\n\n- Employee deferral: $576.92 \u00d7 6% = **$34.62**\n- Employer match: $576.92 \u00d7 4% = **$23.08** (if the plan matches per payroll)\n\n## Step 4: Taxes\n\n| Item | Basis | Rate | Amount |\n|---|---|---|---|\n| Federal income tax | $576.92 \u2212 $34.62 = $542.30 | 22% | $119.31 |\n| Social Security | $576.92 (401(k) does **not** reduce FICA) | 6.2% | $35.77 |\n| Medicare | $576.92 | 1.45% | $8.37 |\n\n## Step 5: Net Retro Payment\n\n| | Amount |\n|---|---|\n| Gross retro | $576.92 |\n| 401(k) deferral | \u2212$34.62 |\n| Federal income tax | \u2212$119.31 |\n| Social Security | \u2212$35.77 |\n| Medicare | \u2212$8.37 |\n| **Net (before state/local)** | **$378.85** |\n\n## Compliance Checks\n\n1. **Plan definition of compensation.** Confirm the plan includes retro/back pay as eligible comp. Most do for base pay, but check the plan document.\n2. **402(g) limit.** Make sure the deferral doesn't push the employee past the annual limit ($23,500 for 2025, plus catch-up if 50+).\n3. **Year of payment.** Retro is taxed and reported in the year it's paid, even if it was earned in the prior year.\n4. **Social Security wage base.** Stop the 6.2% if the employee has already hit the annual cap.\n5. **Hourly or non-exempt employees.** Recalculate overtime at 1.5\u00d7 the *new* rate for all OT hours in the retro periods (FLSA requirement).\n6. **Partial first period.** If the raise took effect mid-period, prorate Period 1 by days or hours.\n7. **Withholding method.** If retro is combined with regular wages instead of paid separately, use the aggregate method.\n\n## To Run",
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