Create an Invoice

https://api.constructiononline.com/api/Invoices?Info={invoiceInfo}

This endpoint allows users to create a new invoice for a project in their ConstructionOnline company account. If successful, the endpoint will return a record of the newly created invoice. The new invoice will be automatically assigned a unique numerical ID called 'ID', which will be used for any future references. The required fields for this endpoint include PRJ_ID, CLIENT_ID, and ITEMS (NAME); all other properties are optional and can be entered during invoice creation.

• Requests
• Responses

Requests

Info: JSON

• Properties to be added to the invoice.
• Required properties for the invoice: PRJ_ID, CLIENT_ID, ITEMS
  • Required properties for the invoice ITEMS: NAME
• Allowed properties for the purchase order: TITLE, INV_DATE, RETAINAGE, STATUS, COM_PRORATED, NOTES, DUE_DATE, TERM_ID, TAX_INCLUDED, RETAINAGE_ENABLED, RETAINAGE_TYPE, RETAINAGE_INVOICE_ID 
  • Allowed properties for the purchase order ITEMS: 

Individual properties for creation should be entered as JSON key-value pairs, as seen below:

{
    "PRJ_ID": 1432504,
    "CLIENT_ID": 906920,
    "INV_DATE" : "2026-07-22T00:00:00",
    "DUE_DATE" : "2026-07-31T00:00:00",
    "ITEMS": [
        {
        "NAME" : "Labor",
        "QTY" : 45.0,
        "RATE" : 62.30
        },
        {
        "NAME" : "Material",
        "QTY" : 250.0,
        "RATE" : 7.50
        }
    ]
}

Example requests in cURL, C#, Python, and JavaScript can be found below:

cURL

# replace {email} with the email address for your ConstructionOnline account
# {password} with your ConstructionOnline password
# {apikey} with your provided API key
# {invoiceInfo} with the information for invoice creation

curl -X POST https://api.constructiononline.com/api/Invoices?Info={invoiceInfo} -u {email}:{password} -H 'APIKey:{apikey}'

C#

/* replace {username} with the email address for your ConstructionOnline account
           {password} with your ConstructionOnline password
           {apikey} with your provided API key 
           {invoiceInfo} with the information for invoice creation */
        

public string MakeRequest(string endpoint, string payload) {
     string username = {username};
     string password = {password};
     string apiKey = {apikey};
     string response = "";
      var handler = new HttpClientHandler() { AutomaticDecompression = System.Net.DecompressionMethods.GZip };
          using (HttpClient client = new HttpClient(handler)) {
           client.BaseAddress = new Uri("http://api.constructiononline.com");
           client.DefaultRequestHeaders.Accept.Clear();
           client.DefaultRequestHeaders.Accept.Add(new MediaTypeWithQualityHeaderValue("application/json"));
           client.DefaultRequestHeaders.Authorization = new AuthenticationHeaderValue("Basic", System.Convert.ToBase64String(System.Text.Encoding.GetEncoding("ISO-8859-1").GetBytes(username + ":" + password)));
           client.DefaultRequestHeaders.Add("APIKey", apiKey);
           client.DefaultRequestHeaders.Add("Accept-Encoding", "gzip");
           HttpContent content = new StringContent(payload, System.Text.Encoding.UTF32, "application/json");
           response = client.PostAsync(endpoint, content).Result.ToString();
            }
      return response;
            }

     MakeRequest("api/Invoices?Info={invoiceInfo}");

Python

#replace {username} with the email address for your ConstructionOnline account
#{password} with your ConstructionOnline password
#{apikey} with your provided API key
#{invoiceInfo} with the information for invoice creation


import base64, requests, json
#Global Variables
  apikey = {apikey}
  username = {username}
  password = {password}

#Functions
  def makeRequest(endpoint, payload):
       url = "https://api.constructiononline.com/" + endpoint
       userPass = username + ":" + password    
       headers = {
                    "APIKey": apikey,
                    "Accept-Encoding": "gzip, deflate, br",
                    "Authorization": "Basic " + base64.b64encode(userPass.encode()).decode(),
                }
       response = requests.request("POST", url, headers=headers, data=payload)
       return json.dumps(json.loads(response.text), indent=2)   
#Main Program 
print(makeRequest("api/Invoices?Info={invoiceInfo}"))

JavaScript

/* replace {username} with the email address for your ConstructionOnline account
           {password} with your ConstructionOnline password
           {apikey} with your provided API key 
           {invoiceInfo} with the information for invoice creation */
     

 username = '{username}';
 password = '{password}';
 apikey = '{apikey}';

 function makeRequest(endpoint, payload) {
          auth = btoa('${username}:${password}');
          var myHeaders = new Headers();
          myHeaders.append("APIKey", apikey);
          myHeaders.append("Accept-Encoding", "gzip, deflate, br");
          myHeaders.append("Authorization", "Basic ${auth}");

                var requestOptions = {
                    method: 'POST',
                    body: '',
                    headers: myHeaders,
                    redirect: 'follow'
                };
                fetch("https://api.constructiononline.com/" + endpoint, requestOptions)
                    .then(response => response.text())
                    .then(result => console.log(result))
                    .catch(error => console.log('error', error));
                return response;
            };
 makeRequest("api/Invoices?Info={invoiceInfo}");

Responses

200: Success

A successful request will return a 200 response with a record of the newly created invoice in the body.

A sample response and property definitions can be found here.

404: Error

The server was not able to locate the resource specified in the request.

429: Error

The user has surpassed the request rate limit for the hour, day, week, or month.

500: Error

There was an internal server error and the server was unable to complete the request.

Last updated: July 22, 2026