Sales Tax API Quickstart

This quickstart takes you from an API key to a filed-ready transaction in about five minutes. It’s part of the sales tax API documentation and works the same whether you’re using a trial key or a production key.

Need a key? Get a free 30-day trial key — no credit card or sales call — or copy your production key from your Zamp account.

Get your API key

Use a free trial key (preconfigured with all 47 remote-seller state registrations) to explore and test, or production access through your Zamp account when you’re ready to go live.

Authenticate

Pass your API key as a bearer token in the Authorization header on every request. See Authentication for details.

curl https://api.zamp.com/transactions \
  -H "Authorization: Bearer {your-api-key}"

Calculate tax on a transaction

Send a transaction to POST /calculations. The shipToAddress determines the taxing jurisdictions, and each line item’s productTaxCode determines taxability — see Tax codes to find the right codes for your catalog.

curl -X POST https://api.zamp.com/calculations \
  -H "Authorization: Bearer {your-api-key}" \
  -H "Content-Type: application/json" \
  -d '{
    "id": "123",
    "name": "INV-123",
    "transactedAt": "2023-07-01T00:00:00.000Z",
    "isResale": false,
    "discount": 2,
    "subtotal": 18,
    "shippingHandling": 5,
    "total": 23,
    "shipToAddress": {
      "line1": "120 SW 10TH AVE",
      "line2": null,
      "state": "KS",
      "city": "TOPEKA",
      "zip": "66612"
    },
    "lineItems": [
      {
        "id": "LI-123",
        "amount": 10,
        "quantity": 2,
        "discount": 0,
        "shippingHandling": 0,
        "productName": "The Ultimate Sampler",
        "productSku": "SAMPLER-100",
        "productTaxCode": "R_TPP_FOOD-BEVERAGE_HOME-CONSUMPTION"
      }
    ]
  }'

const response = await fetch("https://api.zamp.com/calculations", {
  method: "POST",
  headers: {
    "Authorization": "Bearer {your-api-key}",
    "Content-Type": "application/json",
  },
  body: JSON.stringify({
    id: "123",
    name: "INV-123",
    transactedAt: "2023-07-01T00:00:00.000Z",
    isResale: false,
    discount: 2,
    subtotal: 18,
    shippingHandling: 5,
    total: 23,
    shipToAddress: {
      line1: "120 SW 10TH AVE",
      line2: null,
      state: "KS",
      city: "TOPEKA",
      zip: "66612",
    },
    lineItems: [
      {
        id: "LI-123",
        amount: 10,
        quantity: 2,
        discount: 0,
        shippingHandling: 0,
        productName: "The Ultimate Sampler",
        productSku: "SAMPLER-100",
        productTaxCode: "R_TPP_FOOD-BEVERAGE_HOME-CONSUMPTION",
      },
    ],
  }),
});

const calculation = await response.json();
console.log(calculation.taxDue);

import requests

response = requests.post(
    "https://api.zamp.com/calculations",
    headers={"Authorization": "Bearer {your-api-key}"},
    json={
        "id": "123",
        "name": "INV-123",
        "transactedAt": "2023-07-01T00:00:00.000Z",
        "isResale": False,
        "discount": 2,
        "subtotal": 18,
        "shippingHandling": 5,
        "total": 23,
        "shipToAddress": {
            "line1": "120 SW 10TH AVE",
            "line2": None,
            "state": "KS",
            "city": "TOPEKA",
            "zip": "66612",
        },
        "lineItems": [
            {
                "id": "LI-123",
                "amount": 10,
                "quantity": 2,
                "discount": 0,
                "shippingHandling": 0,
                "productName": "The Ultimate Sampler",
                "productSku": "SAMPLER-100",
                "productTaxCode": "R_TPP_FOOD-BEVERAGE_HOME-CONSUMPTION",
            },
        ],
    },
)

print(response.json()["taxDue"])

The response returns the total taxDue plus one entry per taxing jurisdiction — state, county, and district — for each line item and for shipping. Abridged here; see the Calculations reference for the full response.

Response (abridged)

{
  "id": "123",
  "name": "INV-123",
  "taxDue": 1.58,
  "taxes": [
    {
      "lineItemId": "LI-123",
      "state": "KS",
      "jurisdictionCode": "KS.S.20",
      "jurisdictionName": "KANSAS",
      "jurisdictionDivision": "STATE",
      "taxableAmount": 18,
      "taxRate": 0.04,
      "taxDue": 0.72
    },
    {
      "lineItemId": "LI-123",
      "state": "KS",
      "jurisdictionCode": "KS.C.177",
      "jurisdictionName": "SHAWNEE COUNTY",
      "jurisdictionDivision": "COUNTY",
      "taxableAmount": 18,
      "taxRate": 0.0135,
      "taxDue": 0.243
    }
  ]
}

Post the transaction for filing

Once the sale completes, persist it with POST /transactions using the same transaction shape. This is the core calculate, then post workflow behind every Zamp integration — calculations quote the tax, posted transactions become the returns Zamp files.

Next steps

Calculations and transactions

The recommended workflows for quoting tax and recording sales.

Transaction object

Every field on the object behind calculations and transactions.

Tax codes

Map your products to the right taxability rules.

Errors

Status codes and error formats you’ll want to handle.

Before going live, review Certifying your integration to make sure your build handles every customer scenario.

Last modified on August 21, 2026

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Sales Tax API Quickstart

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Transaction object

Tax codes

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Calculations and transactions

Transaction object

Tax codes

Errors

Next steps