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The calculation object contains tax rate information with support for per-unit line item pricing, IP-based tax resolution, origin addresses, metadata passthrough, and enhanced tax jurisdiction detail. A calculation also includes a calculation_id that you’ll use to record a transaction for filing.

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When to create Calculations

Calculations should be used any time you need to calculate sales tax before charging a customer for a transaction. Most e-commerce clients will submit a POST to /tax/calculations during their checkout flow after the end customer has submitted their address, but before collecting payment. core flow

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How to create Calculations

curl --request POST \
  --url https://api.numeralhq.com/tax/calculations \
  --header 'Authorization: Bearer <token>' \
  --header 'Content-Type: application/json' \
  --header 'X-API-Version: 2026-03-01' \
  --data '{
  "customer": {
    "address": {
      "address_city": "Nashville",
      "address_country": "US",
      "address_line_1": "123 Broadway",
      "address_postal_code": "37203",
      "address_province": "TN",
      "address_type": "billing"
    }
  },
  "metadata": {
    "payment_id": "68407cb7-e1fa-47fa-8244-bd9411d53c61"
  },
  "order_details": {
    "automatic_tax": "auto",
    "customer_currency_code": "USD",
    "line_items": [
      {
        "amount": 1000000,
        "product_category": "BEVERAGES",
        "quantity": 1
      },
      {
        "amount": 1000000,
        "product_category": "GENERAL_MERCHANDISE",
        "quantity": 1
      }
    ],
    "tax_included_in_amount": false
  },
  "origin_address": {
    "address_city": "Nashville",
    "address_country": "US",
    "address_line_1": "500 Church St",
    "address_line_2": "",
    "address_postal_code": "37219",
    "address_province": "TN"
  }
}'

{
  "testmode": true,
  "id": "calc_17725956342644181bdd4-5975-44d5-8c96-05233f565fdd",
  "object": "tax.calculation",
  "customer_currency_code": "USD",
  "line_items": [
    {
      "line_item_id": "li_1772595634232f1d34578-aed2-42cb-a917-09b2c8322b20",
      "product": {
        "reference_line_item_id": "",
        "reference_product_id": "default-beverages",
        "reference_product_name": "Default BEVERAGES Product",
        "product_tax_code": "BEVERAGES"
      },
      "tax_jurisdictions": [
        {
          "tax_rate": 0.04,
          "tax_due_decimal": 40000,
          "fee_amount": 0,
          "rate_type": "FOOD_AND_DRUG STATE SALES TAX",
          "tax_authority_name": "Tennessee",
          "tax_authority_type": "",
          "tax_type": "SALES"
        },
        {
          "tax_rate": 0.0225,
          "tax_due_decimal": 3600,
          "fee_amount": 0,
          "rate_type": "FOOD_AND_DRUG CITY LOCAL SALES TAX",
          "tax_authority_name": "Place 52006, TN",
          "tax_authority_type": "",
          "tax_type": "SALES"
        },
        {
          "tax_rate": 0.005,
          "tax_due_decimal": 800,
          "fee_amount": 0,
          "rate_type": "FOOD_AND_DRUG DISTRICT LOCAL SALES TAX",
          "tax_authority_name": "Other Special Applications 91951",
          "tax_authority_type": "",
          "tax_type": "SALES"
        }
      ],
      "tax_amount": 44400,
      "amount_excluding_tax": 1000000,
      "amount_including_tax": 1044400,
      "quantity": 1
    },
    {
      "line_item_id": "li_177259563426441045f22-c55e-4a4b-a1b9-e880b1d6a7b0",
      "product": {
        "reference_line_item_id": "",
        "reference_product_id": "default-general-merchandise",
        "reference_product_name": "Default GENERAL_MERCHANDISE Product",
        "product_tax_code": "GENERAL_MERCHANDISE"
      },
      "tax_jurisdictions": [
        {
          "tax_rate": 0.0275,
          "tax_due_decimal": 4400,
          "fee_amount": 0,
          "rate_type": "SINGLE_ARTICLE STATE SALES TAX",
          "tax_authority_name": "Tennessee",
          "tax_authority_type": "",
          "tax_type": "SALES"
        },
        {
          "tax_rate": 0.07,
          "tax_due_decimal": 70000,
          "fee_amount": 0,
          "rate_type": "GENERAL STATE SALES TAX",
          "tax_authority_name": "Tennessee",
          "tax_authority_type": "",
          "tax_type": "SALES"
        },
        {
          "tax_rate": 0.0225,
          "tax_due_decimal": 3600,
          "fee_amount": 0,
          "rate_type": "GENERAL CITY LOCAL SALES TAX",
          "tax_authority_name": "Place 52006, TN",
          "tax_authority_type": "",
          "tax_type": "SALES"
        },
        {
          "tax_rate": 0.005,
          "tax_due_decimal": 800,
          "fee_amount": 0,
          "rate_type": "GENERAL DISTRICT LOCAL SALES TAX",
          "tax_authority_name": "Other Special Applications 91951",
          "tax_authority_type": "",
          "tax_type": "SALES"
        }
      ],
      "tax_amount": 78800,
      "amount_excluding_tax": 1000000,
      "amount_including_tax": 1078800,
      "quantity": 1
    }
  ],
  "total_tax_amount": 123200,
  "tax_included_in_amount": false,
  "total_amount_excluding_tax": 2000000,
  "total_amount_including_tax": 2123200,
  "expires_at": 1772682034,
  "metadata": {
    "payment_id": "68407cb7-e1fa-47fa-8244-bd9411d53c61"
  },
  "customer": {
    "type": "CONSUMER"
  },
  "automatic_tax": "auto",
  "address_resolution_status": "EXACT",
  "address_used": {
    "address_line_1": "500 Church St",
    "address_line_2": "",
    "address_city": "Nashville",
    "address_province": "TN",
    "address_postal_code": "37219",
    "address_country": "US"
  }
}
We return both the aggregate tax information as well as a detailed breakdown for each line item. Many users will just use the total_tax_amount to identify what to charge a user, but you will always have the details as you need them. For IP-based calculations, see the IP-Based Tax Resolution section below.
Breaking Change (from 2026-01-01): The amount field on line items represents the per-unit price. The taxable base is calculated as amount x quantity. This is a change from versions prior to 2026-01-01 where amount represented the total line item value.

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Request Parameters

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Customer Object

{
  "customer": {
    "id": "cus_123456789", // Optional customer ID
    "address": {
      "address_line_1": "123 Broadway",
      "address_line_2": "", // Optional
      "address_city": "Nashville",
      "address_province": "TN",
      "address_postal_code": "37203",
      "address_country": "US",
      "address_type": "billing" // "shipping" or "billing"
    },
    "type": "CONSUMER", // "BUSINESS" or "CONSUMER" (default if omitted)
    "tax_ids": [ // Required for BUSINESS (except US), not allowed for CONSUMER
      {
        "type": "eu_vat", // Stripe-style tax ID type (439+ types supported)
        "value": "DE123456789"
      }
    ]
  }
}
  • address (object): Optional if customer.ip is provided. At least one of address or ip must be present.
  • ip (object): New in 2026-03-01. See IP-Based Tax Resolution below.
  • type (string): Customer type affecting tax calculation.
    • CONSUMER (default) - Individual consumer, standard B2C tax calculations
    • BUSINESS - Business entity requiring tax IDs for B2B tax logic
  • tax_ids (array): Required for BUSINESS customers (except US), not allowed for CONSUMER customers.
    • type (string): Stripe-style tax ID type. 439+ types supported including us_ein, eu_vat, gb_vat, au_abn, ca_bn, jp_cn, and many more.
    • value (string): Valid tax identification number

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Origin Address

{
  "origin_address": {
    "address_line_1": "500 Church St",
    "address_line_2": "", // Optional
    "address_city": "Nashville",
    "address_province": "TN",
    "address_postal_code": "37219",
    "address_country": "US"
  }
}
The ship-from address used for origin-based tax jurisdictions. Required for accurate tax calculation in states that use origin-based sourcing rules.

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Order Details

{
  "order_details": {
    "customer_currency_code": "USD", // Supports 32 currencies
    "tax_included_in_amount": false,
    "automatic_tax": "auto", // "auto" or "disabled"
    "line_items": [
      {
        "reference_line_item_id": "line_123456789", // Optional
        "reference_product_id": "p-1233543", // Required if no product_category
        "product_category": "GENERAL_MERCHANDISE", // Required if no reference_product_id
        "amount": 1000000, // Per-unit price in smallest currency unit (e.g., cents)
        "quantity": 1 // Taxable base = amount x quantity
      }
    ]
  }
}
  • amount (number): Per-unit price in the currency’s smallest unit (e.g., cents for USD). The taxable base is amount x quantity.
  • automatic_tax (string): Controls tax collection and registration behavior.
    • auto - Return tax rates everywhere you have an active registration
    • disabled - Always return 0 tax regardless of thresholds

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Metadata

{
  "metadata": {
    "payment_id": "68407cb7-e1fa-47fa-8244-bd9411d53c61"
  }
}
Optional. Store arbitrary key-value pairs for your own reference. Values must be strings of 255 characters or fewer. Metadata is echoed back in the response unchanged.

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Features from 2026-01-01

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Per-Unit Line Item Pricing

The amount field on line items now represents the per-unit price rather than the total line item value. The taxable base is calculated as amount x quantity.
Versionamount MeaningExample: 3 items at $25.00 each
2025-05-12 and earlierTotal line item value"amount": 7500, "quantity": 3
2026-01-01+Per-unit price"amount": 2500, "quantity": 3

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Enhanced Tax Jurisdiction Detail

Tax jurisdiction objects in the response now include richer detail from the tax engine:
FieldTypeDescription
tax_due_decimalnumberTax amount due for this jurisdiction in the currency’s smallest unit
tax_authority_namestringName of the tax authority (e.g., “Tennessee”, “ALLEGHENY”)
tax_authority_typestringType of authority (e.g., “STATE”, “COUNTY”, “CITY”, “DISTRICT”)
tax_typestringType of tax: SALES, USE, VAT, or GST
rate_typestringDescriptive rate classification (e.g., “GENERAL STATE SALES TAX”, “FOOD_AND_DRUG CITY LOCAL SALES TAX”)
The jurisdiction_name and note fields from prior versions are no longer included in 2026-01-01+ responses.

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Origin Address Support

You can now provide an origin_address representing the ship-from location. This is used for origin-based tax jurisdictions where the seller’s location affects the applicable tax rate.

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Address Resolution

Responses include information about how the address was resolved:
  • address_resolution_status (string): Indicates the precision of the address match.
ValueDescription
EXACTExact street-level address match
POSTAL_FALLBACK_1Fell back to postal code-level match
POSTAL_ONLYOnly postal code was used for resolution
  • address_used (object): The resolved address that was actually used for the tax calculation.

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Expanded Tax ID Types

Tax ID types have been expanded from 2 types (VAT, GST) to 439+ Stripe-style types. Examples include us_ein, eu_vat, gb_vat, au_abn, ca_bn, jp_cn, in_gst, br_cnpj, and many more.

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Standard Error Format

Error responses use a flat format: 
{
  "code": 400,
  "type": "PRODUCT_NOT_FOUND",
  "message": "Product not found"
}
This replaces the nested format ({ "error": { "code": "...", "message": "..." } }) from versions prior to 2026-01-01.

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IP-Based Tax Resolution (New in 2026-03-01)

Starting with API version 2026-03-01, you can provide a customer IP address instead of a full street address. The API will geo-resolve the IP to determine the taxable location.

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The customer.ip Object

{
  "customer": {
    "type": "CONSUMER",
    "ip": {
      "value": "217.217.113.167",   // IPv4 or IPv6
      "resolution": "strict"         // "strict", "zero", "approximate", or "best_effort"
    }
  }
}
At least one of customer.address or customer.ip must be provided. If both are given, the address is used first with IP as a fallback.

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Resolution Modes

ModeBehavior
strict (default)Error if IP cannot resolve to sufficient detail for tax calculation
zeroReturn zero-rate response if resolution is insufficient
approximateAttempts to resolve the IP to an address using heuristics
best_effortTry approximate first, fall back to zero rates
Numeral strongly recommends using strict mode to stay as compliant as possible.

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New Response Fields

Responses include additional fields when using this API version:
FieldTypeDescription
location_sourcestring"address" or "ip" — which input was used for tax determination
resolution_precisionstringPrecision level: STREET, POSTAL_PLUS, POSTAL, PROVINCE, COUNTRY, or APPROXIMATED
address_usedobjectThe resolved address that was actually used for tax calculation
curl --request POST \
  --url https://api.numeralhq.com/tax/calculations \
  --header 'Authorization: Bearer <token>' \
  --header 'Content-Type: application/json' \
  --header 'X-API-Version: 2026-03-01' \
  --data '{
  "customer": {
    "type": "CONSUMER",
    "ip": {
      "value": "217.217.113.167",
      "resolution": "strict"
    }
  },
  "order_details": {
    "customer_currency_code": "USD",
    "tax_included_in_amount": false,
    "automatic_tax": "auto",
    "line_items": [
      {
        "product_category": "SAAS_GENERAL",
        "reference_line_item_id": "ip-test-001",
        "amount": 10000,
        "quantity": 5
      }
    ]
  }
}'

{
  "testmode": true,
  "id": "calc_17725714816806a81b828-0757-4ec2-9307-3c1001733f73",
  "object": "tax.calculation",
  "customer_currency_code": "USD",
  "line_items": [
    {
      "line_item_id": "li_17725714816804066f7e8-06ad-4286-9070-ad90991246d0",
      "product": {
        "reference_line_item_id": "ip-test-001",
        "reference_product_id": "default-saas-general",
        "reference_product_name": "Default SAAS_GENERAL Product",
        "product_tax_code": "SAAS_GENERAL"
      },
      "tax_jurisdictions": [
        {
          "tax_rate": 0.06,
          "tax_due_decimal": 3000,
          "fee_amount": 0,
          "rate_type": "GENERAL STATE SALES TAX",
          "tax_authority_name": "Pennsylvania",
          "tax_authority_type": "",
          "tax_type": "SALES"
        },
        {
          "tax_rate": 0.01,
          "tax_due_decimal": 500,
          "fee_amount": 0,
          "rate_type": "GENERAL COUNTY LOCAL SALES TAX",
          "tax_authority_name": "ALLEGHENY",
          "tax_authority_type": "",
          "tax_type": "SALES"
        }
      ],
      "tax_amount": 3500,
      "amount_excluding_tax": 50000,
      "amount_including_tax": 53500,
      "quantity": 5
    }
  ],
  "total_tax_amount": 3500,
  "tax_included_in_amount": false,
  "total_amount_excluding_tax": 50000,
  "total_amount_including_tax": 53500,
  "expires_at": 1772657881,
  "customer": {
    "type": "CONSUMER"
  },
  "automatic_tax": "auto",
  "address_resolution_status": "POSTAL_ONLY",
  "address_used": {
    "address_line_1": "",
    "address_line_2": "",
    "address_city": "",
    "address_province": "PA",
    "address_postal_code": "15212",
    "address_country": "US"
  },
  "location_source": "ip",
  "resolution_precision": "POSTAL"
}

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IP Resolution Errors

When using strict mode, the API returns a 422 error if the IP cannot be resolved to sufficient detail for tax calculation. 
curl --request POST \
  --url https://api.numeralhq.com/tax/calculations \
  --header 'Authorization: Bearer <token>' \
  --header 'Content-Type: application/json' \
  --header 'X-API-Version: 2026-03-01' \
  --data '{
  "customer": {
    "type": "CONSUMER",
    "ip": {
      "value": "2600:387:2:803::81",
      "resolution": "strict"
    }
  },
  "order_details": {
    "customer_currency_code": "USD",
    "tax_included_in_amount": false,
    "automatic_tax": "auto",
    "line_items": [
      {
        "product_category": "SAAS_GENERAL",
        "amount": 10000,
        "quantity": 1
      }
    ]
  }
}'

{
  "code": 422,
  "type": "IP_RESOLUTION_INSUFFICIENT_US",
  "message": "IP address resolved to US-GA but could not determine a postal code. Please provide customer.address with address_postal_code and address_province."
}
Error TypeHTTP CodeDescription
INVALID_IP_FORMAT400ip.value is not a valid IPv4 or IPv6 address
IP_RESOLUTION_FAILED422IP could not be resolved to any country
IP_RESOLUTION_INSUFFICIENT_US422IP resolved to a US state but no postal code could be determined
IP_RESOLUTION_INSUFFICIENT_CA422IP resolved to Canada but no province could be determined
To avoid resolution errors, use resolution: "best_effort" or resolution: "zero" instead of strict. These modes will return a zero-rate response when resolution is insufficient rather than an error.

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Further documentation

The full documentation for creating calculations is on this page.