QuickBooks Online API - Sales tax: trying to override automatic sales tax, but it's not respecting my inputs - api

Question

QBOnline API: Problems with overriding Sales Tax - passed in values not respected on Invoice (AST seems to override my override)
Hi all,
Yes, I'm new to the API. Diving in head first! :)
I'm trying to troubleshoot a problem with my app. It's submitting new Invoices to the QBOnline API, and passing in all the line item information. We aren't trying to use the AST system - so I was trying to set the override values. (Documentation: https://developer.intuit.com/app/developer/qbo/docs/workflows/manage-sales-tax-for-us-locales#specifying-sales-tax)
I think that I am providing the values correctly, but the system is still calculating it's own sales tax amount.
Target API URL:
https://sandbox-quickbooks.api.intuit.com/v3/company/4620816365232674520/Invoice?minorversion=4
Here's an example of the object we are passing in (edited for privacy, expanded for human readability):
{
"BillAddr": {
"City": "AnywhereVille",
"Country": "USA",
"CountrySubDivisionCode": "CA",
"Line1": "",
"Line2": "Customer Name LLP",
"Line3": "45 E. Pacific Coast Highway",
"Line4": "",
"PostalCode": "90804"
},
"CustomField": [{
"DefinitionId": "1",
"Name": "P.O. Number",
"StringValue": "",
"Type": "StringType"
}, {
"DefinitionId": "2",
"Name": "Sales Rep",
"StringValue": "TY",
"Type": "StringType"
}],
"CustomerMemo": {
"value": "Pay your invoice online at: ..."
},
"CustomerRef": {
"value": "60"
},
"DocNumber": "11111",
"DueDate": "2022-08-01",
"Line": [{
"Amount": 576,
"Description": "",
"DetailType": "SalesItemLineDetail",
"LineNum": 1,
"SalesItemLineDetail": {
"ClassRef": {
"name": "3 Studios",
"value": "1111111111111"
},
"ItemRef": {
"name": "16GBUSBFLASH",
"value": "21"
},
"Qty": 48,
"TaxCodeRef": {
"value": "TAX"
},
"UnitPrice": 12
}
}, {
"Amount": 168,
"Description": "",
"DetailType": "SalesItemLineDetail",
"LineNum": 4,
"SalesItemLineDetail": {
"ClassRef": {
"name": "3 Studios",
"value": "1111111111111"
},
"ItemRef": {
"name": "DVDMEDIA",
"value": "23"
},
"Qty": 12,
"TaxCodeRef": {
"value": "TAX"
},
"UnitPrice": 14
}
}, {
"Amount": 600,
"Description": "",
"DetailType": "SalesItemLineDetail",
"LineNum": 6,
"SalesItemLineDetail": {
"ClassRef": {
"name": "3 Studios",
"value": "1111111111111"
},
"ItemRef": {
"name": "DIGITALDEL30",
"value": "25"
},
"Qty": 12,
"TaxCodeRef": {
"value": "TAX"
},
"UnitPrice": 50
}
}],
"SalesTermRef": {
"value": "8"
},
"TxnDate": "2022-08-01",
"TxnTaxDetail": {
"TaxLine": [{
"Amount": 130.98,
"DetailType": "TaxLineDetail",
"TaxLineDetail": {
"NetAmountTaxable": 576,
"PercentBased": true,
"TaxPercent": 0.0925,
"TaxRateRef": {
"value": "4"
}
}
}],
"TotalTax": 130.98,
"TxnTaxCodeRef": {
"value": "4"
}
}
}