“I'll probably have to go to an accountant this year.”

In the past, you have done your taxes on your own. But you started a business this year, so your financial situation is more complicated than in the past. You think you'll need an accountant to help you. You are talking with a friend about taxes, and you say:

I'll probably have to go to an accountant this year.

(someone) will probably have to (do something)

Use this expression when you're not sure, but you think someone will have to do something in the future. Here's another example:

Mark will probably have to work on that day, but he should be free on the following weekend.

go to (a professional)

To "go to a ___" means to visit a professional to get service from them. Here are some other examples:

Have you gone to a doctor?

I think you need to go to a mechanic.

an accountant

An accountant is a person whose job is to calculate information about people's or companies' money. One of the jobs of an accountant is to do taxes.