I'm trying to create Sales Orders and Invoices via Acumatica ERP's REST API.
For some reason I'm getting error only for creation of the Invoices through I'm using almost the same JSON's for both:

Here is my RestService:

```
public class RestService : IDisposable
{
    private readonly HttpClient _httpClient;

    private readonly string _acumaticaBaseUrl;

    #region Ctor
    public RestService(string acumaticaBaseUrl, string userName, string password, string company, string branch, string locale)
    {
        _acumaticaBaseUrl = acumaticaBaseUrl;
        _httpClient = new HttpClient(
            new HttpClientHandler
            {
                UseCookies = true,
                CookieContainer = new CookieContainer()
            })
        {
            BaseAddress = new Uri(acumaticaBaseUrl + "/entity/Default/6.00.001/"),
            DefaultRequestHeaders =
            {
                Accept = {MediaTypeWithQualityHeaderValue.Parse("text/json") }
            }
        };

        //Log in to Acumatica ERP
        _httpClient.PostAsJsonAsync(
          acumaticaBaseUrl + "/entity/auth/login", new
          {
              name = userName,
              password = password,
              company = company,
              branch = branch,
              locale = locale
          }).Result
            .EnsureSuccessStatusCode();
    }

    void IDisposable.Dispose()
    {
        _httpClient.PostAsync(_acumaticaBaseUrl + "/entity/auth/logout",
          new ByteArrayContent(new byte[0])).Wait();
        _httpClient.Dispose();
    }
    #endregion
    //Data submission
    public string Put(string entityName, string parameters, string entity)
    {
        var res = _httpClient.PutAsync(_acumaticaBaseUrl + "/entity/Default/6.00.001/" + entityName + "?" + parameters, new StringContent(entity, Encoding.UTF8, "application/json")).Result
            .EnsureSuccessStatusCode();
        return res.Content.ReadAsStringAsync().Result;
    }
}

```

And here is the Main code:

```
using (RestService service = new RestService(ACUMATICA_INSTANCE_URL, USERNAME,PASSWORD,COMPANY, "", "EN-US"))
{
    Console.WriteLine("Login successful");

    string order = @"{  
        ""OrderNbr"":{ value: ""000204"" },
        ""CustomerID"":{ value: ""TESTCST005""},
        ""Details"": [ 
        {
            ""InventoryID"": { value: ""301CMPST02"" },
            ""Quantity"": { value: 10 }
        }]
    }";
    string invoice = @"{  
        ""ReferenceNbr"":{ value: ""001032"" },
        ""CustomerID"":{ value: ""TESTCST005""},
        ""Details"": [ 
        {
            ""InventoryID"": { value: ""DESIGN"" },
            ""Quantity"": { value: 10 }
        }]
    }";

    try
    {
        Console.WriteLine("Trying to create the following Order");
        Console.WriteLine(order);
        string updatedOrder = service.Put("SalesOrder", null, order);
        Console.WriteLine("Order created successful");
        Console.WriteLine(updatedOrder);

        Console.WriteLine("Trying to create the following Invoice");
        Console.WriteLine(invoice);
        string updatedInvoice = service.Put("SalesInvoice", null, invoice);
        Console.WriteLine("Invoice created successful");
        Console.WriteLine(updatedInvoice);
    }
    catch(Exception exc)
    {
        Console.WriteLine(exc.Message);
    }
    Console.ReadLine();
}

```

I'm not able to find out what is the problem. The response I'm getting is always the following:

> 
> "StatusCode: 500, ReasonPhrase: 'Internal Server Error', Version: 1.1, Content: System.Net.Http.StreamContent, Headers:\r\n{\r\n X-Handled-By: Acumatica-PX.Export/AuthenticationManagerModule\r\n Cache-Control: private\r\n Set-Cookie: Locale=TimeZone=GMTM0500G&Culture=en-US; path=/\r\n Set-Cookie: UserBranch=5; path=/\r\n Server: Microsoft-IIS/8.5\r\n X-Powered-By: ASP.NET\r\n Date: Wed, 02 Aug 2017 13:02:49 GMT\r\n Content-Length: 36\r\n Content-Type: text/json; charset=utf-8\r\n}"
> 
> 
> 

I'm able to add the Invoice from Screen with these same values.
Here is the example of using Acumatica ERP REST API to Create a Customer
[Creation of a Record](https://help.acumatica.com/(W(4))/?ScreenId=ShowWiki&pageid=9d966d50-a0a1-4456-a9ff-1cc2159d48d4).