Mandatory e-filing and e-payment
You should file and pay your tax returns electronically using the Revenue Online Service (ROS). You can benefit from an extension to existing deadlines for paying tax and filing returns if you both pay and file using ROS.
The vast majority of Revenue’s business customers are legally obliged to both e-file and e-pay. If you do not use ROS to file your returns and make payments, you may have to pay a penalty. This penalty is €1,520 on each transaction.
You can find detailed information on mandatory e-filing, in the Starting a business section.