---
title: "Create or update an invoice customer"
method: POST
path: "/invoice-customers"
tags: ["Invoicing"]
---

# Create or update an invoice customer

`POST /invoice-customers`

## Request

- Base URL: `https://api.app.lastaccountingcompany.com/portal`
- URL: `https://api.app.lastaccountingcompany.com/portal/invoice-customers`
- Auth: HTTP bearer
- TypeScript: <https://skmtc.dev/lastaccountingcompany/apis/lac-customer-api/docs/invoice-customers/post.ts> (a function with typed inputs; its response is checked against the schema)

Upserts a party in the invoicing counterparty register. Include `id` to update an existing party. Requires a write-scoped key.

## Request body

- Party: An invoicing counterparty (the customer you invoice), with e-invoice routing and per-party defaults. Rates in basis points (25.5% = 2550).
  - `id` string: Party id. Include on upsert to update an existing party.
  - `name` string, required
  - `business_id` string: Finnish business ID (Y-tunnus), e.g. `1234567-8`.
  - `vat_number` string: EU VAT number, e.g. `FI12345678`.
  - `address_line1` string
  - `postal_code` string
  - `city` string
  - `country_code` string: ISO 3166-1 alpha-2, e.g. `FI`.
  - `email` string
  - `einvoice_address` string: E-invoice (verkkolasku) address, e.g. an OVT identifier.
  - `einvoice_operator` string: E-invoice operator/intermediator code.
  - `default_payment_terms_days` integer
  - `default_vat_code` string
  - `default_vat_rate_basis_points` integer: Default VAT rate in basis points (25.5% = 2550).
  - `default_invoice_language` string

## Response `200`

Upserted party.

- Party: An invoicing counterparty (the customer you invoice), with e-invoice routing and per-party defaults. Rates in basis points (25.5% = 2550).
  - `id` string: Party id. Include on upsert to update an existing party.
  - `name` string, required
  - `business_id` string: Finnish business ID (Y-tunnus), e.g. `1234567-8`.
  - `vat_number` string: EU VAT number, e.g. `FI12345678`.
  - `address_line1` string
  - `postal_code` string
  - `city` string
  - `country_code` string: ISO 3166-1 alpha-2, e.g. `FI`.
  - `email` string
  - `einvoice_address` string: E-invoice (verkkolasku) address, e.g. an OVT identifier.
  - `einvoice_operator` string: E-invoice operator/intermediator code.
  - `default_payment_terms_days` integer
  - `default_vat_code` string
  - `default_vat_rate_basis_points` integer: Default VAT rate in basis points (25.5% = 2550).
  - `default_invoice_language` string

## Other responses

- `401`: Missing or invalid bearer token.
- `403`: Insufficient scope or role — e.g. a read-scoped key on a mutating method, or an API key on an admin/approver-only endpoint.

---

[API](https://skmtc.dev/lastaccountingcompany/apis/lac-customer-api.md) - [All operations](https://skmtc.dev/lastaccountingcompany/apis/lac-customer-api/llms.txt) - [OpenAPI document](https://skmtc.dev/lastaccountingcompany/apis/lac-customer-api/revisions/52e277b4f031?raw)