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To verify your integration, compare the API’s output for a fixed set of inputs against values you expect. This checks your request wiring, not the tax math itself, which is maintained by Symmetry.

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Approach

  1. Pin your inputs. Use a fixed request, including an explicit checkDate, so results don’t shift as the current date advances.
  2. Capture the baseline. Record the response content (grossPay, federal, fica, medicare, state, netPay) for that request.
  3. Assert on the fields you care about. Compare each returned amount to your expected value in your test suite.

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What to watch for

  • Pin the checkDate. Tax tables change over time; without a fixed date, expected values drift with each tax update.
  • Match the method. The same wages produce different results across calculators and supplemental settings. Compare like-for-like. See Calculation methods by calculator.
  • Display rounding. Monetary results are returned to two decimals (cents).
If results differ from what you expect, see Calculation differs from expected value.