We are receiving the following error when trying to calculate tax:
"String was not recognized as a valid DateTime."
We have our DocumentDate correctly formatted as YYYY-MM-DD.
Avalara AvaTax - SOAP API
If your DocumentDate is correctly formatted and you are still receiving a String was not recognized as a valid DateTime error that means that there is another Date type field in your request which is improperly formatted.
Please check the dates of each field that require a date field, including the deprecated PaymentDate field that is no longer used for the SOAP API.
Even though the PaymentDate field has been deprecated, sending non-Date information that is improperly formatted in that field will cause the error.