Revenue sometimes unilaterally send out Form 12s to individual taxpayers. It's not necessarily a sign of any problem with your affairs. I must admit that the one and only time that I received one from them a few years ago I was going through a redundancy/unemployment situation and, between one thing and another, I did overlook it. I never heard anything about it since and I have continued to keep my tax affairs up to date by writing to them directly when any significant changes in circumstances arise (whether they be in my favour or theirs!). Not that I'm encouraging others to ignore any Form 12 sent to them by Revenue...