Answer:
a technical specialist in computer software
Explanation:
In this case a technical specialist would be someone that provides expert consultancy on computer software, more specifically tax software. A salesperson is probably very good at getting the attention of the customers and setting the proper mood for a sale, but when you need someone who can answer very technical questions, then you need a technical specialist.
Unless of course the salesperson was a technical specialist in computer software, although the careers are not that compatible. The ability to be able to sell high tech products and know the technical specifications was something that made Steve Jobs unique. But there are not very many Steve Jobs around.