Investments FAQs What is a variable interest rate? A variable interest rate is one that may increase or decrease when interest rates in general change. What is a fixed interest rate? A fixed interest rate stays the same for a set time. It is not affected by changes in interest rates in general. What is net interest? Net interest is the amount of interest paid to you after we have taken off deposit interest retention tax (DIRT). What is gross interest? Gross interest is the amount of interest you earned before we took off deposit interest retention tax (DIRT). What is EAR and AER? EAR stands for ‘equivalent annual rate’ and AER stands for ‘annual equivalent rate’ but they mean the same thing. They are used to show the full price of interest on an account. The higher the EAR or AER, the more interest you will earn. Where can I download the Commission Summary Document? Download the I&I PDF.