I confirmed it many times with the garda station, and then motor tax office by phone, and then at the motor tax office when i was dropping the form.

To be honest I couldn't be bothered finding it as google searches keep returning chats on forums and so on. But feel free to confirm it with your local office, it's just a friendly warning for anybody who thinks they will be saving a month or two of tax. If you definitely need your car on the 3rd month, when you go to tax it you will be asked to pay for the previous 2 even if it's been off the road.

If I find something I'll post it up