Registered letters

High-level description

A registered letter is sensitive content that a recipient opens by signing with BankID. Use it when proof of the opening action and its associated data are needed.

Sub-types

registered.letter is the registered-letter content type; it has no additional sub-types.

Common payload

Set type to registered.letter and include a registered object. Registered letters require an SSN recipient; email matching is not supported.

Field	Purpose
ssn	Identifies the individual recipient
subject	Describes the letter; do not include personal data
registered.expires_at	Limits how long the letter can be opened; no more than 30 days from now
registered.hidden	Controls whether the sender or subject is hidden before opening
registered.sender_reference	Stores your reference in the signed or expired response

{
  "ssn": "YYYYMMDDNNNN",
  "subject": "Important information from Example Energy",
  "type": "registered.letter",
  "registered": {
    "expires_at": "2026-10-01T23:59:59Z",
    "sender_reference": {
      "case_id": "case-123"
    },
    "hidden": {
      "sender": false,
      "subject": false
    }
  }
}

Other information

1. Send a registered letter

Send the common payload with POST /v2/tenant/{tenantKey}/content. The recipient uses BankID to open the letter.

2. Retrieve and manage responses

Retrieve the response status for signed or expired letters, retrieve the individual response when needed, then delete the stored response according to your retention policy.

Retrieve signed and expired response records by tenant and retrieve a particular response by its response key. See the Registered letters API reference for the current request contract.