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PATCH
/
api
/
v1
/
letters
/
{letterId}
curl -X PATCH https://thepostalcompany.com/api/v1/letters/a1b2c3d4-e5f6-7890-abcd-ef1234567890 \
  -H "Authorization: Bearer tpc_your_api_key" \
  -H "Content-Type: application/json" \
  -d '{
    "content": "Dear Jane,\n\nUpdated letter content.\n\nBest regards"
  }'

{
  "id": "a1b2c3d4-e5f6-7890-abcd-ef1234567890",
  "status": "draft",
  "recipient": "Jane Doe",
  "address": {
    "street": "Keizersgracht",
    "number": "123",
    "postalcode": "1015 CJ",
    "city": "Amsterdam",
    "country": "NL"
  },
  "content": "Dear Jane,\n\nUpdated letter content.\n\nBest regards",
  "created_at": "2026-04-14T10:00:00.000Z",
  "updated_at": "2026-04-14T10:01:00.000Z"
}

Documentation Index

Fetch the complete documentation index at: https://docs.thepostalcompany.com/llms.txt

Use this file to discover all available pages before exploring further.

​
Update a Draft

Update a letter that is in draft status. You can modify the recipient, address, content, or any combination. Letters that have already been sent cannot be updated.

​
Path parameters

​
letterId
string
required
The unique letter ID.

​
Request

All fields are optional — only include the fields you want to change.
​
recipient
string
Name of the recipient. Maximum 30 characters.
​
address
object
The recipient’s postal address. If provided, all required address fields must be included.
​
content
string
The letter body text.

​
Response

Returns the full updated letter object (same shape as Get a Letter).

​
Examples

curl -X PATCH https://thepostalcompany.com/api/v1/letters/a1b2c3d4-e5f6-7890-abcd-ef1234567890 \
  -H "Authorization: Bearer tpc_your_api_key" \
  -H "Content-Type: application/json" \
  -d '{
    "content": "Dear Jane,\n\nUpdated letter content.\n\nBest regards"
  }'

{
  "id": "a1b2c3d4-e5f6-7890-abcd-ef1234567890",
  "status": "draft",
  "recipient": "Jane Doe",
  "address": {
    "street": "Keizersgracht",
    "number": "123",
    "postalcode": "1015 CJ",
    "city": "Amsterdam",
    "country": "NL"
  },
  "content": "Dear Jane,\n\nUpdated letter content.\n\nBest regards",
  "created_at": "2026-04-14T10:00:00.000Z",
  "updated_at": "2026-04-14T10:01:00.000Z"
}

​
Error codes

StatusDescription
400Invalid request body
401Missing, invalid, or revoked API key
404Letter not found or does not belong to your account
409Letter is not in draft status