we may use a so-called the first-time abatement (FTA) penalty waiver - assuming you did not have penalties of a “significant” amount assessed in the past.
You will find more details in this publication - http://www.irs.gov/irm/part20/irm_20-001-001r-cont01.html
Criteria for Relief From Penalties
You might also find this publication - http://www.irs.gov/pub/foia/ig/tas/tas-13-0212-007.pdf
So you may simply write a letter attaching it to the tax return - explain your situation that was a honest mistake and soon as you know about filing requirements - you do your best to comply. And you are asking for "the first-time abatement"
At the same time - you may ask to abate penalties from all tax returns
as that was your honest mistake.
Instead of writing a letter - you may use form 843 - that would generally make no difference..
File a form 843 -
to request the "accuracy related penalty" be abate based on reasonable cause. If you provide the reason like "I forgot" - I do not think it will be considered as reasonable - so be careful when prepare an abatement request.
There might be some reason which you woudl not able to foreseen - such as health issues, tax preparer mistake, casualty, etc.
Here are instructions -
If the IRS accepts your reasons as reasonable - and agrees to abate penalties - at least part of the issue would be resolved.