# Invoice

The /api/customers/invoice/ endpoint invoices a number of invoice lines on a customer.

# Parameters

• id string required
  ID of the customer.
• business_entity string
  The external ID of the business entity to invoice for. Must be specified if subscription_id is not given.
• subscription_id string
  If the invoice lines concern a certain subscription.
• period string Defaults to current
  Either current or the index of the period, with 1 being the oldest period, in case a subscription_id is specified, e.g. "period": "1". Note that invoice lines never bind to the subscription directly but always a specific period of the subscription.
• lines array required
  The lines to invoice. See the line attributes below.
• due string
  Date the invoice is due, e.g. 2026-11-09. If not filled in, the due date is calculated from the internal rules in Iteras.
• send boolean Defaults to true
  Set to false to prevent the invoice being sent. This can be useful when importing old debt.
• note string
  Internal note attached to the invoice.

Each element of lines is an object with the following attributes:

• text string required
  Description of what is invoiced, may contain newlines, e.g. Extra service\nLine 2.
• amount integer required
  Integer amount (send €10.50 as 1050), including any tax.
• currency string required
  Three-letter ISO currency code, e.g. EUR. The currency must match the invoice/business entity.
• tax_rate number required
  The tax rate applied to the line, e.g. 0.25 for 25% tax. Set it to 0 for lines that are exempt from tax.

# Examples

Invoice two lines on a subscription period:

POST /api/customers/invoice/ HTTP/1.1
Content-Type: application/json{
  "id": "12345",
  "lines": [{
    "text": "Product A",
    "amount": 10050,
    "currency": "DKK",
    "tax_rate": 0.25
  }, {
    "text": "Shipping",
    "amount": 2050,
    "currency": "DKK",
    "tax_rate": 0
  }],
  "subscription_id": "32142532",
  "due": "2026-11-09"
}

Invoice a balance from an old system, without sending it:

POST /api/customers/invoice/ HTTP/1.1
Content-Type: application/json{
  "id": "12345",
  "lines": [{
    "text": "Unpaid amount from Jan-Feb",
    "amount": 56095,
    "currency": "DKK",
    "tax_rate": 0.25
  }],
  "business_entity": "DKbranch",
  "due": "2026-11-09",
  "send": false,
  "note": "Balance from old system"
}

The endpoint returns the number of the new invoice:

{ "invoice_number": "1007" }

# Errors

Invalid requests due to programming error, e.g. invalid JSON, returns 400. This also covers a missing lines array, a tax_rate outside the range 0-1, and more than one distinct non-zero tax_rate on an invoice.

A well-formed operation where a supplied value is invalid is not executed and returns an HTTP 422 error. The response is a JSON object with the errors keyed by the field they concern, e.g. a currency that doesn't match the business entity:

{
  "lines": ["Invalid currency: EUR"]
}

Errors that are not specific to a field are returned with the empty string as key, e.g. an unknown subscription, period or business entity:

{
  "": ["Business entity does not exist."]
}