Non-Trading Private Ltd Co, Tax Registration, & Annual Return

I set up a private ltd company last year. It never traded, and at the time i did not register it with revenue as i believed that this was only required when trading commenced.

I am happy to voluntarily strikeoff the company. I assume i need to provide a form 11F to do this? Are there any penalties in practice for not registering when no trading took place?

If i wish to keep the company alive, how would i perform the tax return as the ROS uploadable files need a tax id.

you won't need a Form 11F if the company hasn't traded. You will need Revenue clearance regardless. I'd suggest putting voluntary company strike off in Google and you'll get a provider to this for you.