---
title: "Add companies"
method: POST
path: "/lists/{id}/items"
tags: ["Lists"]
---

# Add companies

`POST /lists/{id}/items`

## Request

- Base URL: `https://api.companystack.co.uk`
- URL: `https://api.companystack.co.uk/lists/{id}/items`
- Auth: one of:
  - HTTP bearer
  - API key in header `X-Api-Key`

Adds up to 5,000 companies by number. Companies already on another of your lists use none of your cap. Supplying a reference, note or tags for a company already on the list updates it. When the cap is reached part-way, the rest are returned in `over_limit` (403 if none could be added).

## Path parameters

- `id` integer, required

## Request body

- object
  - `items` object[], required
    - `company_number` string, required: Company number, e.g. 08804411 or SC586124 (shorter numbers are zero-padded)
    - `note` string, nullable
    - `tags` string[], nullable
    - `custom_ref` string, nullable: Your own reference for the company
  - `method` 'search' | 'paste' | 'csv' | 'watch' | 'similar' | 'api': How the companies were chosen (for your activity log); default api

## Response `200`

Nothing new added (already on the list / updated)

## Other responses

- `201`: Added
- `400`: Invalid input; `error` says what to change
- `401`: API key missing, malformed or revoked
- `403`: Plan limit or feature not included
- `404`: List not found (or private to the person who made it)
- `409`: List archived
- `429`: Per-minute or per-day limit reached (`code: rate_limited`, `window: minute|day`). Wait `Retry-After` seconds; when both windows are full the day is reported. A refused request does not count against either limit. A bulk lookup (`POST /company/bulk`) counts each company number in it as one request, so one that is more than you have left is refused whole, and the body adds `requested` and `fits`.

---

[API](https://skmtc.dev/companystack/apis/companystack-api.md) · [All operations](https://skmtc.dev/companystack/apis/companystack-api/llms.txt) · [OpenAPI document](https://skmtc.dev/companystack/apis/companystack-api/revisions/8f3234237d2d?raw)