Discontinued, when true, means that the tax is no longer assessed (read-only).
value = object.isDiscontinued()
|object||A TaxControl or Tax object|
|value||A boolean result|
A tax object is first obtained using Item. If the selected tax is no longer in force, the value returned by this property will be True. The discontinued tax returns a TaxAmount of 0, and is generally kept in tables for at least one year before being removed altogether.