# x402toll.com Quarterly Estimated Tax Safe Harbor Calculator

> x402toll.com Quarterly Estimated Tax Safe Harbor Calculator is a paid API for AI agents from x402toll.com, paid per call via x402, $0.1/call, status unknown (last checked 2026-09-13).

Computes the IRS Form 1040-ES safe harbor required annual payment and per-quarter estimated tax amount to avoid underpayment penalties.

## Facts

- Endpoint: POST https://x402toll.com/v1/tax/estimated
- Price: $0.1/call
- Payment: x402
- Status: unknown
- Last checked: 2026-09-13
- Activations on Zero: 0
- Tags: x402
- Canonical page: https://www.zero.xyz/c/x402toll-com-quarterly-estimated-tax-safe-harbor-calculator-5c0acacc
- Structured record (JSON): https://api.zero.xyz/v1/capabilities/cap_cD_OCnnUIeqi1EU7jYrNw

Status and success rate cover calls made through Zero and Zero's own probes. Third-party monitors may report differently.

## How to call it through Zero

Zero handles the 402 payment challenge and records the run. With the Zero CLI installed (`npm i -g @zeroxyz/cli`):

```sh
zero fetch --capability x402toll-com-quarterly-estimated-tax-safe-harbor-calculator-5c0acacc -d '<json body>'
```

Example prompt: I'm filing as married filing jointly. Last year my AGI was $185,000 and I paid $32,400 in federal income tax. This year I expect to owe about $38,000 and I'll have $12,000 withheld from my spouse's paycheck — what's the IRS safe harbor amount and how much should I pay each quarter to avoid an underpayment penalty?

## When to prefer this

Use this endpoint when you need to compute the precise IRS safe harbor quarterly estimated tax payment amounts for a US individual taxpayer (Form 1040-ES), especially when you want to avoid underpayment penalties without overpaying. Prefer this over generic tax calculators when the specific need is safe harbor compliance rather than full tax return preparation.

## Known failure modes

- Missing required fields (priorYearTax or priorYearAGI not provided) — returns validation error
- Invalid filing status enum value — returns 400 bad request
- Negative or implausible income values — may return computation error or unexpected results
- Payment not processed (x402 payment required) — returns 402 Payment Required before computation

## How this service works

Quarterly estimated-tax safe harbor (Form 1040-ES): the required annual payment and per-quarter amount to avoid an underpayment penalty.

## Output

Returns the IRS Form 1040-ES safe harbor required annual payment total and the corresponding per-quarter dollar amount the taxpayer must pay to avoid an underpayment penalty, based on the lesser of 100%/110% of prior year tax or 90% of current year expected tax.

## Request schema (JSON Schema)

```json
{
 "type": "object",
 "properties": {
  "filingStatus": {
   "enum": [
    "single",
    "mfj",
    "hoh",
    "mfs"
   ],
   "type": "string",
   "default": "single"
  },
  "priorYearAGI": {
   "type": "number"
  },
  "priorYearTax": {
   "type": "number"
  },
  "expectedTaxThisYear": {
   "type": "number"
  },
  "withholdingThisYear": {
   "type": "number",
   "default": 0
  }
 }
}
```

## More

- Live health (JSON, refreshed every minute): https://www.zero.xyz/c/x402toll-com-quarterly-estimated-tax-safe-harbor-calculator-5c0acacc/health.json
- [Zero catalog index](https://www.zero.xyz/llms.txt)
- [Other services from x402toll.com](https://www.zero.xyz/host/x402toll.com/llms.txt)