The first year I had a space in my home fully dedicated to work was 2014. I was probably lax in not inquiring further into the "its not really gonna matter" statement. However, he never asked any questions like how large the space is, does it have a separate phone line etc. Just it doesn't matter
Did you report a loss from your business in 2014 and 2015? It most cases, it would matter.. at least a little bit. You can still amend now. I don't know the person or their knowledge of taxes, but yeah, I would make sure it really doesn't matter before taking their word for it.
You can't claim home office expenses for prior years on your 2016 return. You would need to amend those returns.
Is this is relation to an employee job or a self-employed job? Do you own or rent your home?
In some cases, a home office doesn't qualify. For instance, if your office is your kitchen table or if your work is done almost entirely outside of the home, you might not truly have a home office.
If your net income was very low or below zero, your accountant may have also decided to disregard on account of it not making a difference.
What was the reason for this decision? You obviously discussed it- do you recall the gist of the decision?