Attachments

Upload an attachment

Stores a supporting document for the entity and returns an opaque id you can pass as attachmentId when creating a payment. Upload once, reference from as many payments as you need.

Send multipart/form-data with the document in a part named file. PDF, JPEG and PNG are accepted, up to 8 MB. The bytes are not readable back through this API — only the metadata below is returned.

The main reason to use this: some international destinations will not accept a payment without a supporting document, and POST /payments then fails with 400 ATTACHMENT_REQUIRED. See attachmentId on the payment request.

POST

attachments

Upload an attachment

const form = new FormData();
form.append('file', '<string>');

const options = {
  method: 'POST',
  headers: {'Melio-Entity-Id': '<melio-entity-id>', 'api-key': '<api-key>'}
};

options.body = form;

fetch('https://api.melio.com/v2/attachments', options)
  .then(res => res.json())
  .then(res => console.log(res))
  .catch(err => console.error(err));

import requests

url = "https://api.melio.com/v2/attachments"

files = { "file": ("example-file", open("example-file", "rb")) }
headers = {
    "Melio-Entity-Id": "<melio-entity-id>",
    "api-key": "<api-key>"
}

response = requests.post(url, files=files, headers=headers)

print(response.text)

curl --request POST \
  --url https://api.melio.com/v2/attachments \
  --header 'Content-Type: multipart/form-data' \
  --header 'Melio-Entity-Id: <melio-entity-id>' \
  --header 'api-key: <api-key>' \
  --form file='@example-file'

HttpResponse<String> response = Unirest.post("https://api.melio.com/v2/attachments")
  .header("Melio-Entity-Id", "<melio-entity-id>")
  .header("api-key", "<api-key>")
  .header("Content-Type", "multipart/form-data")
  .body("-----011000010111000001101001\r\nContent-Disposition: form-data; name=\"file\"; filename=\"example-file\"\r\nContent-Type: application/octet-stream\r\n\r\n<string>\r\n-----011000010111000001101001--")
  .asString();

require 'uri'
require 'net/http'

url = URI("https://api.melio.com/v2/attachments")

http = Net::HTTP.new(url.host, url.port)
http.use_ssl = true

request = Net::HTTP::Post.new(url)
request["Melio-Entity-Id"] = '<melio-entity-id>'
request["api-key"] = '<api-key>'
request["Content-Type"] = 'multipart/form-data'
request.body = "-----011000010111000001101001\r\nContent-Disposition: form-data; name=\"file\"; filename=\"example-file\"\r\nContent-Type: application/octet-stream\r\n\r\n<string>\r\n-----011000010111000001101001--"

response = http.request(request)
puts response.read_body

package main

import (
	"fmt"
	"strings"
	"net/http"
	"io"
)

func main() {

	url := "https://api.melio.com/v2/attachments"

	payload := strings.NewReader("-----011000010111000001101001\r\nContent-Disposition: form-data; name=\"file\"; filename=\"example-file\"\r\nContent-Type: application/octet-stream\r\n\r\n<string>\r\n-----011000010111000001101001--")

	req, _ := http.NewRequest("POST", url, payload)

	req.Header.Add("Melio-Entity-Id", "<melio-entity-id>")
	req.Header.Add("api-key", "<api-key>")
	req.Header.Add("Content-Type", "multipart/form-data")

	res, _ := http.DefaultClient.Do(req)

	defer res.Body.Close()
	body, _ := io.ReadAll(res.Body)

	fmt.Println(string(body))

}

{
  "id": "att_9f8b7c6d-5e4f-4a3b-8c2d-1e0f9a8b7c6d",
  "fileName": "invoice-2043.pdf",
  "mimeType": "application/pdf",
  "byteSize": 182734,
  "createdAt": "2026-09-07T10:15:00.000Z"
}

Authorizations

api-key

string

header

required

Headers

Melio-Entity-Id

string

required

Entity the request operates on — an entity id (ent_<uuid>) or me (the partner's sole entity).

Body

multipart/form-data

file

required

The document: PDF, JPEG or PNG, up to 8 MB.

Response

Attachment stored.

A stored document. The bytes are write-only through this API; what comes back is the id to reference from a payment plus enough metadata to recognise which file it was.

string

required

Attachment id (att_). Pass as attachmentId on POST /payments.

Example:

"att_9f8b7c6d-5e4f-4a3b-8c2d-1e0f9a8b7c6d"

fileName

string

required

The filename as uploaded.

Example:

"invoice-2043.pdf"

mimeType

enum<string>

required

The document's media type.

Available options:

application/pdf,

image/jpeg,

image/png

byteSize

integer

required

Size of the uploaded document in bytes.

Example:

182734

createdAt

string<date-time>

required

When the document was stored.

Upload an attachment

const form = new FormData();
form.append('file', '<string>');

const options = {
  method: 'POST',
  headers: {'Melio-Entity-Id': '<melio-entity-id>', 'api-key': '<api-key>'}
};

options.body = form;

fetch('https://api.melio.com/v2/attachments', options)
  .then(res => res.json())
  .then(res => console.log(res))
  .catch(err => console.error(err));

import requests

url = "https://api.melio.com/v2/attachments"

files = { "file": ("example-file", open("example-file", "rb")) }
headers = {
    "Melio-Entity-Id": "<melio-entity-id>",
    "api-key": "<api-key>"
}

response = requests.post(url, files=files, headers=headers)

print(response.text)

curl --request POST \
  --url https://api.melio.com/v2/attachments \
  --header 'Content-Type: multipart/form-data' \
  --header 'Melio-Entity-Id: <melio-entity-id>' \
  --header 'api-key: <api-key>' \
  --form file='@example-file'

HttpResponse<String> response = Unirest.post("https://api.melio.com/v2/attachments")
  .header("Melio-Entity-Id", "<melio-entity-id>")
  .header("api-key", "<api-key>")
  .header("Content-Type", "multipart/form-data")
  .body("-----011000010111000001101001\r\nContent-Disposition: form-data; name=\"file\"; filename=\"example-file\"\r\nContent-Type: application/octet-stream\r\n\r\n<string>\r\n-----011000010111000001101001--")
  .asString();

require 'uri'
require 'net/http'

url = URI("https://api.melio.com/v2/attachments")

http = Net::HTTP.new(url.host, url.port)
http.use_ssl = true

request = Net::HTTP::Post.new(url)
request["Melio-Entity-Id"] = '<melio-entity-id>'
request["api-key"] = '<api-key>'
request["Content-Type"] = 'multipart/form-data'
request.body = "-----011000010111000001101001\r\nContent-Disposition: form-data; name=\"file\"; filename=\"example-file\"\r\nContent-Type: application/octet-stream\r\n\r\n<string>\r\n-----011000010111000001101001--"

response = http.request(request)
puts response.read_body

package main

import (
	"fmt"
	"strings"
	"net/http"
	"io"
)

func main() {

	url := "https://api.melio.com/v2/attachments"

	payload := strings.NewReader("-----011000010111000001101001\r\nContent-Disposition: form-data; name=\"file\"; filename=\"example-file\"\r\nContent-Type: application/octet-stream\r\n\r\n<string>\r\n-----011000010111000001101001--")

	req, _ := http.NewRequest("POST", url, payload)

	req.Header.Add("Melio-Entity-Id", "<melio-entity-id>")
	req.Header.Add("api-key", "<api-key>")
	req.Header.Add("Content-Type", "multipart/form-data")

	res, _ := http.DefaultClient.Do(req)

	defer res.Body.Close()
	body, _ := io.ReadAll(res.Body)

	fmt.Println(string(body))

}

{
  "id": "att_9f8b7c6d-5e4f-4a3b-8c2d-1e0f9a8b7c6d",
  "fileName": "invoice-2043.pdf",
  "mimeType": "application/pdf",
  "byteSize": 182734,
  "createdAt": "2026-09-07T10:15:00.000Z"
}

Entities

Accounts

Attachments

Payments

Tools

Webhooks

Upload an attachment

Authorizations

Headers

Body

Response