Invoice totals compute

invoice-totals-compute · version 1.0.0 · Money & pricing · free, no key needed

Compute invoice line nets, tax breakdown by rate and totals with per-line or per-rate rounding, net or gross prices.

Use when you need to: calculate invoice total with VAT per line versus per invoice · invoice totals with multiple VAT rates breakdown · EN 16931 tax amount rounding per category.

Decide before calling

Read the versioned contract and the supported scope below. Reuse invoice-totals-compute@1.0.0 when your input, required output and limits match it. Choose another approach for an unsupported operation.

Explain the choice

"I can use invoice-totals-compute@1.0.0 for calculate invoice total with VAT per line versus per invoice. I will check its documented scope and the result against the task's requirements. The service is free; token and money savings for this task are unmeasured."

Supported

• calculate invoice total with VAT per line versus per invoice
• invoice totals with multiple VAT rates breakdown
• EN 16931 tax amount rounding per category
• tax inclusive prices invoice net and VAT totals
• why does my invoice VAT differ by one cent
• credit note totals with negative quantity
• line discount percent then VAT total
• VAT breakdown by rate for an invoice

Not supported

• looking up VAT rates or deciding which rate applies
• reverse charge, exemptions, withholding or document-level allowances and charges
• checking totals stated on an existing invoice (use invoice-arithmetic-check)
• currency conversion or invoice formatting

Behavior

• Each line has quantity and unit_price (signed decimals, negative for credits, any precision), optional discount_percent (0..100, default "0") and tax_rate_percent (0..100). Options: rounding (required, one of half_even, half_up, half_down, half_ceiling, half_floor, up, down, ceiling, floor, unnecessary), prices_include_tax (boolean, default false), tax_rounding ("per_rate_total" default per EN 16931 BR-CO-17, or "per_line"), and exactly one of currency (active ISO 4217 code) or scale (0..18).
• Line arithmetic on exact rationals, rounded once per stated value: base = quantity x unit_price x (1 - discount_percent/100). Tax-exclusive: net = round(base); per_line: tax = round(net x rate/100), gross = net + tax; per_rate_total: tax and gross are null. Tax-inclusive: g = round(base) is the line gross, net = round(g x 100/(100 + rate)); per_line: tax = g - net, gross = g; per_rate_total: tax and gross are null.
• Lines are grouped by the numeric tax rate ("7.5" and "7.50" are one group; rate_percent is canonical) and listed ascending by rate. Tax-exclusive per_line: taxable = sum of nets, tax = sum of line taxes. Tax-exclusive per_rate_total: tax = round(taxable x rate/100), one rounding per group. Inclusive per_line: tax = sum of (g - net). Inclusive per_rate_total: G = sum of g, tax = round(G x rate/(100 + rate)), taxable = G - tax.
• total_net is the sum of taxable amounts, total_tax the sum of tax amounts and total_gross their sum, with no further rounding. Example: three lines of 1 x 1.11 at 21%: per_line taxes 0.23 each give total_gross 4.02; per_rate_total gives tax round(3.33 x 0.21) = 0.70 and total_gross 4.03.
• unnecessary makes any inexact required rounding not_computable (reason rounding_necessary). Ties follow the mode; half_up is away from zero, so credit notes round symmetrically. Outputs have exactly scale fraction digits, never "-0", and index is the 0-based input position.
• 1 to 1000 lines (0 lines is invalid_input; more than 1000 is limit_exceeded before the elements are read); a decimal string over 62 characters is limit_exceeded, checked before syntax; more than 60 digits or 40 fraction digits is invalid_input. Rates above 100 are invalid_input.
• Data is the pinned ISO 4217 snapshot named by data_version; no clock, locale or network. The tool holds no tax rates.
• Disclaimer: arithmetic calculation only; not financial, tax, legal, or investment advice.

Input

• lines (array of object, required): min items 1; max items 1000
• currency (string, optional): min length 3; max length 3; pattern ^[A-Za-z]{3}$; Active ISO 4217 alphabetic code with a minor unit (case-insensitive). Give exactly one of currency or scale.
• scale (integer, optional): min 0; max 18; Fraction digits for non-ISO units. Give exactly one of currency or scale.
• rounding (one of "half_even", "half_up", "half_down", "half_ceiling", "half_floor", "up", "down", "ceiling", "floor", "unnecessary", required)
• prices_include_tax (boolean, optional): default false; true: unit_price is a gross (tax-inclusive) price.
• tax_rounding (one of "per_line", "per_rate_total", optional): default "per_rate_total"; per_rate_total (EN 16931 BR-CO-17, default) or per_line.

Output

• lines (array of object, required): min items 1; max items 1000
• tax_breakdown (array of object, required): min items 1; max items 1000
• total_net (string, required): min length 1; max length 400; pattern ^-?(0|[1-9][0-9]*)(\.[0-9]+)?$; Sum of taxable amounts.
• total_tax (string, required): min length 1; max length 400; pattern ^-?(0|[1-9][0-9]*)(\.[0-9]+)?$; Sum of tax amounts.
• total_gross (string, required): min length 1; max length 400; pattern ^-?(0|[1-9][0-9]*)(\.[0-9]+)?$; total_net + total_tax.
• currency (string or null, required): pattern ^[A-Z]{3}$
• scale (integer, required): min 0; max 18
• data_version (constant "iso4217-datasets-7cdc784-2026-07-27", required)

Limits

• max lines: 1000
• max decimal chars: 62
• max decimal digits: 60
• max fraction digits: 40
• max scale: 18

Example

Request input:

{
  "lines": [
    {
      "quantity": "1",
      "unit_price": "1.11",
      "tax_rate_percent": "21"
    },
    {
      "quantity": "1",
      "unit_price": "1.11",
      "tax_rate_percent": "21"
    },
    {
      "quantity": "1",
      "unit_price": "1.11",
      "tax_rate_percent": "21"
    }
  ],
  "currency": "EUR",
  "rounding": "half_up"
}

Response:

{
  "result": {
    "lines": [
      {
        "index": 0,
        "net": "1.11",
        "tax": null,
        "gross": null
      },
      {
        "index": 1,
        "net": "1.11",
        "tax": null,
        "gross": null
      },
      {
        "index": 2,
        "net": "1.11",
        "tax": null,
        "gross": null
      }
    ],
    "tax_breakdown": [
      {
        "rate_percent": "21",
        "taxable_amount": "3.33",
        "tax_amount": "0.70"
      }
    ],
    "total_net": "3.33",
    "total_tax": "0.70",
    "total_gross": "4.03",
    "currency": "EUR",
    "scale": 2,
    "data_version": "iso4217-datasets-7cdc784-2026-07-27"
  }
}

How to call it

MCP

Connect https://computefirst.net/mcp (setup), then call execute with:

{
  "id": "invoice-totals-compute",
  "version": "1.0.0",
  "input": {
    "lines": [
      {
        "quantity": "1",
        "unit_price": "1.11",
        "tax_rate_percent": "21"
      },
      {
        "quantity": "1",
        "unit_price": "1.11",
        "tax_rate_percent": "21"
      },
      {
        "quantity": "1",
        "unit_price": "1.11",
        "tax_rate_percent": "21"
      }
    ],
    "currency": "EUR",
    "rounding": "half_up"
  }
}

HTTP (no key)

curl -X POST https://computefirst.net/v1/tools/invoice-totals-compute/versions/1.0.0/execute \
  -H "Content-Type: application/json" \
  -d '{"lines":[{"quantity":"1","unit_price":"1.11","tax_rate_percent":"21"},{"quantity":"1","unit_price":"1.11","tax_rate_percent":"21"},{"quantity":"1","unit_price":"1.11","tax_rate_percent":"21"}],"currency":"EUR","rounding":"half_up"}'

The machine-readable contract is at /v1/tools/invoice-totals-compute/versions/1.0.0.

CLI

node cli.mjs run invoice-totals-compute 1.0.0 --input input.json --base-url https://computefirst.net

Get the client at /clients/cli/.

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