Hi Marcos
1) You are correct. A long while back, I contributed an update to the Information Framework (the SID) that defined how taxes and tax exemptions should be represented across the entire model. In the Open API this adoption has been limited to the area of tax exemption for parties and account. We really do need to extend this to the catalog and inventory.
2) Why would the amount and rate be mutually exclusive? True, for a simple tax definition the rate defines the amount, but why should we be miserly and expect the consumer to calculate. For a complex tax definition, it is possible that the amount is calculated by an external tax engine and the rate is a reflection of that calculation.
Hope it helps
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Jonathan Goldberg
Amdocs Management Limited
Any opinions and statements made by me on this forum are purely personal, and do not necessarily reflect the position of the TM Forum or my employer.
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