> ## Documentation Index
> Fetch the complete documentation index at: https://docs.symmetry.com/llms.txt
> Use this file to discover all available pages before exploring further.

# Model 401(k) and 403(b) contribution changes

> Show the paycheck impact of changing a retirement contribution.

The `401k` and `403b` calculators show how a change in retirement contribution affects take-home pay (and, in the widget, retirement projections).

## Request

POST to `401k` (or `403b`) with the wage inputs plus the contribution fields:

```bash theme={null}
curl -X POST https://calculators.symmetry.com/api/calculators/401k \
  -H "pcc-api-key: yourKey" -H "Content-Type: application/json" \
  -d '{"state":"AZ","grossPay":2000,"grossPayType":"PAY_PER_PERIOD","payFrequency":"BI_WEEKLY","grossPayYTD":0,"federalFilingStatusType":"SINGLE","federalAllowances":0,"additionalFederalWithholding":0,"employeeContribution":6,"employeeContributionType":"PERCENT_OF_GROSS"}'
```

## Contribution fields

| Field                                               | Meaning                                                                                   |
| --------------------------------------------------- | ----------------------------------------------------------------------------------------- |
| `employeeContribution` / `employeeContributionType` | The employee's contribution amount and whether it's `PERCENT_OF_GROSS` or `FIXED_AMOUNT`. |
| `employerContribution` / `employerContributionType` | Employer match amount and type.                                                           |
| `contributionLimit`                                 | The limit up to which the employer matches.                                               |
| `olderThan50`                                       | Enables catch-up contributions.                                                           |

To show a "before vs after," run the calculation twice, once at the current contribution and once at the proposed one, then compare `netPay`. For all fields and valid values, see [Object model and default properties](/cbs/api/object-model).

<Note>
  A `457` deferred-comp calculator exists in the API model (mirrors 401(k)) but has no dedicated endpoint or widget. See [Available calculators](/cbs/overview/available-calcs).
</Note>