{
 "task_id": "T06",
 "run": 2,
 "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: Late-Approved Raise with 401(k) Deferral\n\nYou didn't give the employee's figures, so below is the **method**, a **worked example with assumed numbers**, and a list of the details I need to run the real calculation.\n\n## Assumptions for This Example\n\n| Item | Assumed Value |\n|---|---|\n| Pay frequency | Biweekly (6 weeks = 3 pay periods) |\n| Employee type | Salaried, exempt (no overtime) |\n| Old annual salary | $78,000 |\n| New annual salary | $84,500 |\n| Raise effective date | First day of Period 1 (no proration) |\n| 401(k) election | 6% of eligible pay, pre-tax |\n| Plan definition of compensation | Includes retro pay (most plans do, but check the plan document) |\n| Federal withholding method | 22% flat supplemental rate (retro paid as a separate line item) |\n| State income tax | 5% flat (illustrative only) |\n| Employer match | 50% of deferrals up to 6% of pay |\n\n## Step 1: Retro Gross Pay per Period\n\n| | Annual | Biweekly (\u00f726) |\n|---|---|---|\n| New salary | $84,500 | $3,250.00 |\n| Old salary | $78,000 | $3,000.00 |\n| **Difference per period** | | **$250.00** |\n\n| Period | Paid | Should Have Been Paid | Retro Owed |\n|---|---|---|---|\n| 1 | $3,000.00 | $3,250.00 | $250.00 |\n| 2 | $3,000.00 | $3,250.00 | $250.00 |\n| 3 | $3,000.00 | $3,250.00 | $250.00 |\n| **Total** | | | **$750.00** |\n\n## Step 2: 401(k) Deferral on Retro Pay\n\n$750.00 \u00d7 6% = **$45.00**\n\nThe deferral is applied when the retro pay is actually paid. It does not go back into the prior periods.\n\n## Step 3: Taxable Wage Bases\n\n| Wage Base | Calculation | Amount |\n|---|---|---|\n| Federal income tax wages | $750 \u2212 $45 | $705.00 |\n| Social Security / Medicare wages | 401(k) does **not** reduce FICA | $750.00 |\n| State wages (most states) | $750 \u2212 $45 | $705.00 |\n\n## Step 4: Withholdings and Net Pay\n\n| Line | Calculation | Amount |\n|---|---|---|\n| Retro gross | | $750.00 |\n| 401(k) deferral | 6% \u00d7 $750 | \u2212$45.00 |\n| Federal income tax | 22% \u00d7 $705 | \u2212$155.10 |\n| Social Security | 6.2% \u00d7 $750 | \u2212$46.50 |\n| Medicare | 1.45% \u00d7 $750 | \u2212$10.88 |\n| State income tax | 5% \u00d7 $705 | \u2212$35.25 |\n| **Net retro pay** | | **$457.27** |\n\n## Step 5: Employer-Side Costs\n\n| Item | Calculation | Amount |\n|---|---|---|\n| Employer Social Security | 6.2% \u00d7 $750 | $46.50 |\n| Employer Medicare | 1.45% \u00d7 $750 | $10.88 |\n| 401(k) match | 50% \u00d7 $45 | $22.50 |\n| **Total employer cost beyond gross** | | **$79.88** |\n\nAlso add FUTA/SUTA if the employee hasn't reached the annual wage base.\n\n## Items to Check Before Processing\n\n1. **Mid-period effective date.** If the raise started partway through Period 1, prorate that period by working days or by calendar days, following company policy.\n2. **Hourly or non-exempt employees.** Recalculate overtime at the new rate. The retro amount is (new rate \u2212 old rate) \u00d7 all hours, with overtime hours multiplied at 1.5\u00d7.\n3. **Flat-dollar 401(k) elections.** If the employee defers a fixed dollar amount per paycheck instead of a percentage, retro pay may get no deferral. Follow the plan document.\n4. **Annual limits.** Confirm the deferral doesn't push the employee over the IRS 402(g) limit. Also check whether compensation is near the 401(a)(17) cap or the Social Security wage base.\n5. **True-up match.** If the plan calculates the match per pay period, make sure the match on the retro amount is actually funded.\n6. **Supplemental vs. aggregate method.** If the retro amount is combined with regular wages without being separately identified, you must use the aggregate method instead of the 22% flat rate.\n7. **State rules.** Some states do not exclude 401(k) deferrals from state wages. Pennsylvania is one example, which would make the state tax $37.50 instead of $35.25. A few states also have deadlines for paying retro amounts.\n8. **Benefits tied to salary.** Life insurance, disability premiums, and HSA or FSA amounts may also need retro adjustment.\n\n## To Run the Actual Numbers, Send Me:\n\n- Old and new rate (annual salary or hourly)\n- Pay frequency and the exact effective date\n- Hours worked by period, including overtime, if the employee is hourly\n- 401(k) election (percentage or flat dollar, pre-tax or Roth) and match formula\n- Work state, and locality if applicable\n- Year-to-date 401(k) deferrals and year-to-date wages",
 "usage": {
  "input_tokens": 63,
  "cache_creation_input_tokens": 0,
  "cache_read_input_tokens": 0,
  "cache_creation": {
   "ephemeral_5m_input_tokens": 0,
   "ephemeral_1h_input_tokens": 0
  },
  "output_tokens": 2420,
  "output_tokens_details": {
   "thinking_tokens": 625
  },
  "service_tier": "standard",
  "inference_geo": "global"
 }
}