Hi Dean,
The simulation tool doesn't include any coding for the Tax Statement. By no means all of the standard Customs messages have yet been coded either - I guess the developers are too busy to provide a complete service, and the program is not fully supported.
But you can add your own code, as the comments at the top of the program suggest.
However, for such a simple thing as the Tax Statement, I don't think it would be worthwhile. Aside from a few header fields like the FTO, all you need is to map the AAB segments and you should have it working. Let us know if you need any specific help.
One possible complication I notice is that some Message Types (e.g. for USA) expect the SCD iDoc, rather than the standard CCECUS02.
Regards,
Dave