Customer attributes not saving on Add - intuit-partner-platform

Question

So I've been experimenting with adding customers to QuickBooks Online from a local database instance at our business. I want to keep track of our internal customer reference numbers in QBO, so have tried to save those to several different attributes like AcctNum, ExternalKey, ExternalId, AlternateId, or even directly to the Id attribute. After attempting to save to these fields, the return result looks good.
var qbCustomer = new Customer
{
AcctNum = customer.CustRef.ToString(CultureInfo.InvariantCulture),
ExternalKey = new IdType {idDomain = idDomainEnum.NG, Value = customer.CustRef.ToString(CultureInfo.InvariantCulture)},
Id = new IdType {idDomain = idDomainEnum.NG, Value = customer.CustRef.ToString(CultureInfo.InvariantCulture)},
Name = customer.CustName1,
FamilyName = customer.CustRef.ToString(CultureInfo.InvariantCulture),
};
Customer resultCustomer = dataServices.Add(qbCustomer);
But the next time I retrieve those customers, all of those fields are just null. Why are these fields not saving? Is there another more appropriate field to use to store an external ID besides just using one of the plain text fields (Name, Address, etc.)?
UPDATE:
Here's the raw XML exchange.
What I sent when adding a new customer:
<?xml version="1.0" encoding="utf-8"?>
<q1:Customer xmlns="http://www.intuit.com/sb/cdm/qbo" xmlns:q1="http://www.intuit.com/sb/cdm/v2">
<q1:Id>7</q1:Id>
<q1:ExternalKey>7</q1:ExternalKey>
<q1:TypeOf>Person</q1:TypeOf>
<q1:Name>Customer Name</q1:Name>
<q1:FamilyName>7</q1:FamilyName>
<q1:AcctNum>7</q1:AcctNum>
</q1:Customer>
Intuit's response:
<?xml version="1.0" encoding="UTF-8" standalone="yes"?>
<Customer xmlns="http://www.intuit.com/sb/cdm/v2" xmlns:qbp="http://www.intuit.com/sb/cdm/qbopayroll/v1" xmlns:qbo="http://www.intuit.com/sb/cdm/qbo">
<Id idDomain="QBO">12</Id>
<SyncToken>0</SyncToken>
<MetaData><CreateTime>2013-07-25T13:51:43-07:00</CreateTime><LastUpdatedTime>2013-07-25T13:51:43-07:00</LastUpdatedTime></MetaData>
<Name>Customer Name</Name>
<WebSite/>
<Email/>
<FamilyName>7</FamilyName>
<CustomField xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance" xsi:type="StringTypeCustomField"><DefinitionId>Preferred Delivery Method</DefinitionId><Value>DONT</Value></CustomField>
<CustomField xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance" xsi:type="StringTypeCustomField"><DefinitionId>Resale Number</DefinitionId></CustomField>
<CustomField xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance" xsi:type="BooleanTypeCustomField"><DefinitionId>Bill With Parent</DefinitionId><Value>false</Value></CustomField>
<ShowAs>Erik Kunze/Magdalena Guarda Munoz</ShowAs>
<OpenBalance><Amount>0</Amount></OpenBalance>
</Customer>
My retrieval later:
<?xml version="1.0" encoding="UTF-8" standalone="yes"?>
<qbo:SearchResults xmlns="http://www.intuit.com/sb/cdm/v2" xmlns:qbp="http://www.intuit.com/sb/cdm/qbopayroll/v1" xmlns:qbo="http://www.intuit.com/sb/cdm/qbo">
<qbo:CdmCollections xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance" xsi:type="Customers">
<Customer>
<Id idDomain="QBO">12</Id>
<SyncToken>0</SyncToken>
<MetaData><CreateTime>2013-07-25T13:51:43-07:00</CreateTime><LastUpdatedTime>2013-07-25T13:51:43-07:00</LastUpdatedTime></MetaData>
<Name>Customer Name</Name>
<WebSite/>
<Email/>
<FamilyName>7</FamilyName>
<CustomField xsi:type="BooleanTypeCustomField"><DefinitionId>Bill With Parent</DefinitionId><Value>false</Value></CustomField>
<CustomField xsi:type="StringTypeCustomField"><DefinitionId>Preferred Delivery Method</DefinitionId><Value>DONT</Value></CustomField>
<ShowAs>Erik Kunze/Magdalena Guarda Munoz</ShowAs>
<OpenBalance><Amount>0</Amount></OpenBalance>
</Customer>
</qbo:CdmCollections>
<qbo:Count>1</qbo:Count>
<qbo:CurrentPage>1</qbo:CurrentPage>
</qbo:SearchResults>
There's no AcctNum in the raw XML anywhere.

Answer 1

You are referring QBD's customer endpoint in apiexplorer.
Correct QBO link - https://developer.intuit.com/apiexplorer?apiname=V2QBO#Customer
Api Docs & Sample Create request - https://developer.intuit.com/docs/0025_quickbooksapi/0050_data_services/v2/0400_quickbooks_online/customer#Sample_Create_Request_XML
Simplest request body to create QBO customer -
<Customer xmlns:ns2="http://www.intuit.com/sb/cdm/qbo" xmlns="http://www.intuit.com/sb/cdm/v2" xmlns:ns3="http://www.intuit.com/sb/cdm/baseexceptionmodel/xsd">
<TypeOf>Person</TypeOf>
<Name>TestQBCustomer12345</Name>
</Customer>
Simplest Response
<?xml version="1.0" encoding="UTF-8" standalone="yes"?>
<Customer xmlns="http://www.intuit.com/sb/cdm/v2" xmlns:qbp="http://www.intuit.com/sb/cdm/qbopayroll/v1" xmlns:qbo="http://www.intuit.com/sb/cdm/qbo">
<Id idDomain="QBO">14</Id>
<SyncToken>0</SyncToken>
<MetaData>
<CreateTime>2013-07-25T14:08:49-07:00</CreateTime>
<LastUpdatedTime>2013-07-25T14:08:49-07:00</LastUpdatedTime>
</MetaData>
<Name>TestQBCustomer12345</Name>
<WebSite/>
<Email/>
<CustomField xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance" xsi:type="StringTypeCustomField">
<DefinitionId>Preferred Delivery Method</DefinitionId>
<Value>DONT</Value>
</CustomField>
<CustomField xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance" xsi:type="StringTypeCustomField">
<DefinitionId>Resale Number</DefinitionId>
</CustomField>
<CustomField xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance" xsi:type="BooleanTypeCustomField">
<DefinitionId>Bill With Parent</DefinitionId>
<Value>false</Value>
</CustomField>
<ShowAs>TestQBCustomer12345</ShowAs>
<OpenBalance>
<Amount>0</Amount>
</OpenBalance>
</Customer>
You can test it first using apiexplorer then use the proper setters to do the same in your code.
Please let me know how it goes.
Thanks

Answer 2

Refer to the documentation:
https://developer.intuit.com/docs/0025_quickbooksapi/0050_data_services/v2/0500_quickbooks_windows/0600_object_reference/customer
You'll note that:
Id is an internal key generated by IPP/IDS - it's NOT something you can set yourself.
ExternalKey is the same situation - it's generated by IPP/IDS, not set-able by you.
ExternalId is marked "UNSUPPORTED FIELD."
AlternateId is marked "NOT SUPPORTED."
The only one of these fields that should work is:
AcctNum
If you're still having problems with that field, the way to troubleshoot is to get the raw XML outgoing request from Intuit, the raw XML that you get back (showing success) and then the raw response that you get back when you query it, showing that it's NULL.