I've not even submitted my income information to my accountant yet. I have been waiting for certificates from the various income sources just to be sure that the information is correct. The deadline used to be in May with the exact date depending on the last digit of your ΑΦΜ, i.e. 1 near the beginning of May and 9 and zero near the end. For the last couple of years or so it has been later because the government couldn't get the system working on time, probably because they couldn't agree what the rates were. I'm not sure what the deadline will be this year.