If you have not previously filed a Canadian tax return, you will not have that information and will not be able to create a MyAccount till after you have filed a return. Your first return will need to be sent in by post so that the Canada Revenue Agency (CRA) will now be able to enter your information and create a file for you. Once you have a file with the CRA you will be able to create a MyAccount and you will also have the information requested on your filed return or Notice of Assessment which the CRA will send you after the assessment of your return.