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POST
/
tax
/
calculations
curl --request POST \
  --url https://api.numeralhq.com/tax/calculations \
  --header 'Authorization: Bearer <token>' \
  --header 'Content-Type: application/json' \
  --header 'X-API-Version: <x-api-version>' \
  --data '
{
  "customer": {
    "address": {
      "address_line_1": "4 Privet Drive",
      "address_city": "Little Whining",
      "address_province": "CA",
      "address_postal_code": "90210",
      "address_country": "US",
      "address_type": "shipping"
    }
  },
  "order_details": {
    "customer_currency_code": "USD",
    "tax_included_in_amount": false,
    "line_items": [
      {
        "reference_product_id": "wand_elder_12",
        "amount": 10000,
        "quantity": 1
      }
    ]
  }
}
'
{
  "id": "calc_1726683504829b84b2ad6-a4c9-4e0e-986f-7bb3d1fb17c9",
  "object": "tax.calculation",
  "customer_currency_code": "USD",
  "line_items": [
    {
      "product": {
        "reference_product_name": "Elder Wand",
        "reference_product_id": "wand_elder_12",
        "product_tax_code": "GENERAL_MERCHANDISE"
      },
      "tax_jurisdictions": [
        {
          "tax_rate": 0.1,
          "rate_type": "SALES TAX",
          "jurisdiction_name": "California",
          "fee_amount": 0
        }
      ],
      "quantity": 1,
      "tax_amount": 1000,
      "amount_excluding_tax": 10000,
      "amount_including_tax": 11000
    }
  ],
  "tax_included_in_amount": false,
  "total_tax_amount": 1000,
  "total_amount_excluding_tax": 10000,
  "total_amount_including_tax": 11000,
  "expires_at": 1726683511,
  "testmode": true,
  "address_resolution_status": "EXACT",
  "address_used": {
    "address_line_1": "4 Privet Drive",
    "address_city": "Little Whinging",
    "address_province": "CA",
    "address_postal_code": "90210",
    "address_country": "US"
  }
}
Get tax information for a given product and address.

​
cURL Header Example

Use X-API-Version explicitly in requests: 
curl --request POST \
  --url https://api.numeralhq.com/tax/calculations \
  --header 'Authorization: Bearer <token>' \
  --header 'Content-Type: application/json' \
  --header 'X-API-Version: 2026-01-01' \
  --data '{ ... }'
New in 2026-01-01: The amount field on line items is now per-unit price (taxable base = amount x quantity). Responses include origin_address, metadata, address_resolution_status, address_used, and enhanced tax_jurisdictions fields.

​
Per-Unit Pricing

Starting with version 2026-01-01, the amount field on line items represents the per-unit price rather than the total line item value: 
{
  "amount": 2500,  // $25.00 per unit
  "quantity": 3    // taxable base = $75.00
}
If you are migrating from 2025-05-12 or earlier, you must update your integration to send per-unit prices instead of total line item values.

​
New Response Fields

FieldDescription
address_resolution_statusEXACT, POSTAL_FALLBACK_1, or POSTAL_ONLY — precision of the address match
address_usedThe resolved address that was actually used for tax calculation
metadataEchoed back from the request unchanged

​
Enhanced Tax Jurisdictions

Tax jurisdiction objects now include richer detail:
FieldDescription
tax_due_decimalTax amount for this jurisdiction in the currency’s smallest unit
tax_authority_nameName of the tax authority (e.g., “Tennessee”, “ALLEGHENY”)
tax_authority_typeType of authority (e.g., “STATE”, “COUNTY”, “CITY”, “DISTRICT”)
tax_typeType of tax: SALES, USE, VAT, or GST
rate_typeDescriptive rate classification (e.g., “GENERAL STATE SALES TAX”)
The jurisdiction_name and note fields from prior versions are no longer included.

​
Error Format

Error responses now use a flat format: { "code": number, "type": "ERROR_TYPE", "message": "..." }.

Error Codes Reference

See the complete list of error types and their meanings.

Authorizations

​
Authorization
string
header
required

Bearer authentication header of the form Bearer <token>, where <token> is your auth token.

Headers

​
X-API-Version
enum<string>
required

API version to use.

Available options:
2026-03-01,
2026-01-01,
2025-05-12,
2024-09-01

Body

application/json
​
customer
object
required

Customer details. At least one of address or ip must be provided.

​
origin_address
object
required

Required from API version 2025-05-12+. The address that a product is shipped from.

​
order_details
object
required
​
metadata
object

You can store arbitrary keys and values in the metadata. Any valid JSON object whose values are less than 255 characters long is accepted.

Response

Calculate response

​
id
string

The ID of the calculation. You will use this to create a transaction.

Example:

"calc_123456789"

​
object
string

The type of object: tax.calculation.

Example:

"tax.calculation"

​
customer_currency_code
string

The ISO-4217 currency code of the transaction.

Example:

"USD"

​
customer
object

Customer information returned in the response.

​
automatic_tax
enum<string>

The automatic tax setting for this calculation.

Available options:
auto,
disabled
Example:

"auto"

​
line_items
object[]
​
tax_included_in_amount
boolean
Example:

false

​
total_tax_amount
number

Total tax to charge on this calculation.

Example:

14

​
total_amount_excluding_tax
number

Total sale charge, excluding tax.

Example:

200

​
total_amount_including_tax
number

Total sale charge plus tax. What you should charge your customer.

Example:

214

​
expires_at
number

Epoch datetime representing the date and time the tax rates are valid until.

Example:

1714787673

​
testmode
boolean

True if using a production API key. False if using a test API key.

Example:

"false"

​
address_resolution_status
enum<string>

Status of address resolution for the customer address. EXACT: exact address match found, POSTAL_FALLBACK_1: used postal code fallback, POSTAL_ONLY: only postal code was used for tax calculation.

Available options:
EXACT,
POSTAL_FALLBACK_1,
POSTAL_ONLY
Example:

"EXACT"

​
address_used
object

The actual address used for tax calculation after resolution.

​
metadata
object

You can store arbitrary keys and values in the metadata. Any valid JSON object whose values are less than 255 characters long is accepted.

​
location_source
enum<string>

Which input was used for tax determination.

Available options:
address,
ip
Example:

"address"

​
resolution_precision
enum<string>

The precision level of the resolved location.

Available options:
STREET,
POSTAL_PLUS,
POSTAL,
PROVINCE,
COUNTRY,
APPROXIMATED
Example:

"POSTAL"