I would say not with tax law anywhere. It is very complex and has all sorts of interactions between things - e.g. double tax treaties.
That said, a lot more people would probably use complex constructs if they were not so expensive to set up because of the advice needed. I just do not think LLMs help.
RAG are quite good with tax codes. That’s not particularly surprising you have documents telling you exactly what can be done and what is hard is knowing everything inside and putting everything together. That’s pretty much exactly in the sweet spot for LLM queries.
That said, a lot more people would probably use complex constructs if they were not so expensive to set up because of the advice needed. I just do not think LLMs help.