Both the AAT and the ACCA have many similarities. They both are associated with accounting and they are both associations. However, there are a few differences. The AAT stands for the Association of Accounting Technicians. They have over one hundred thousand members. It seems to have begun around the 1980s. It remains strong today. The ACCA stands for the Association of Chartered Certified Accountants. It was founded in 1904.
Therefore, the biggest difference is when they were created and actually the ACCA helped the AAT until it broke away from it. They are two different associations that have accountants join it. One was founded long before the other one and helped the other for a short period of time until it wanted to create another association.