The interview process is very thorough. They first bring you in for an "open house" with other potential candidates and go through the company and position. There are 2-3 members of management/employees to explain everything and try to give you an idea of what it's like. The organization is very unique and most of the work is completed at home, but they have strict procedures to ensure the quality of work.
If you are still interested after the open house, you must take an accounting exam immediately after. If you pass, within a few days they will bring you in for an interview. You will meet with 3 members of management. They ask a few questions about your experience and expectations, but it's more conversation style than rigid interview style.
A few days later they may call to offer you a position. Once you accept, you will go through a training process that is one day a week on-site, and then several hours of "homework" for a few weeks.