TaxNumber type field
Contact entity has a field to store Tax number type (EIN, SSN, ITIN and ATIN). This field is accessible via UI or in exported csv file, but not accessible via API, while "Tax Number" itself can be read using API.
Chris Go commented
This was not a problem with the old OAuth 1.0 "PrivateApp" but since that was deprecated finally a couple of weeks ago, we just migrated our code to OAuth 2.0 and some of our Contacts were getting updated but a couple broke the API will give you a validation error if you try to save a different format for the contact. In the USA, it is fairly common for a Contact that use their SSN (xxx-xx-xxxx) to "upgrade" to a EIN format (xx-xxxxxxx) https://community.xero.com/developer/discussion/13402153
This is not only important, but ridiculous that this field is not included as part of the API. We created an integration with our system to sync the TaxNumber information to Xero. We then have a third party pull the information to process 1099's at the end of the year. Without this the 1099s cannot be processed and adds a mandatory manual step. This seems like oversight that this field was missed when adding the TaxNumber and should not be a feature request but rather elevated to a BUG fix.
Andy Gambles commented
Not particularly the reading that is a problem. Th emain issue is that the EU VAT Return does not have the countries populated when the TaxNumber is supplied via the API. Ths is a glarign ommission and needs resolving.