TAX line is not creating when tax rate is ZERO

Hi,
My customer is using SABRIX as third party TAX application in R12.
They found when AR transaction has the line which has ZERO tax rate, the tax line is not created in R12.
In R11i, they said tax line was automatically created even the line has ZERO tax rate.

Question:
1) Is it expected behavior ? If not, please let us know what Setup or profile option will be preventing this.
2) How can Oracle research further of this issue ?
I found following notes ;
Tax Calculation: Is Sabrix A Supported Vendor For Oracle Receivables? (Doc ID 390123.1)
Oracle E-Business Tax Now Validated With Four Tax Partners (