If you sold the car on that long ago and have never heard anything about it. Its probably scraped or sitting up somewhere.
As you sold it, taxing it etc is not your problem. However when you sold it as the owner at the time you were obliged to fill in the tax book/ registration document and forward it to the dept of the transport at Shannon.

If in the future and problems arise with the car for motoring offences/ tolls you can go to a solicitor and swear an affidavit that you sold the car. ( Details You recall etc) Which they will forward to Shannon to update records.

It up to the power that be to follow up on it then.

This I know as a family friend had issues when he sold a car to a grand lad and gave him the log book.