Retirement tax questions

On this same topic.  I moved from the UK to USA in 2016, and have not contributed to my UK pension plan since leaving the UK.  I have no income from the pension as it is sitting dormant until I start withdrawing from it which may be another 20 years away. 

 

I was not aware of the need to report this on my US taxes, and I had not even thought of it - out of sight out of mind. 

Do I need to amend my taxes and specifically form 8938 and FBAR for previous years, or can I just start doing it for this year.  

 

Thanks in advance.