YOU MUST KEEP HMRC UPDATED WITH YOUR CONTACT DETAILS
In one recent case, a person owed just £40 in tax but did not stay in contact resulting in an escalated tax bill 3 years later of £1,600 (in this case the perosn was able to appeal some of the penalties due to extenuating circumstances.
It is not HMRC's fault.
It is your fault if you do not keep them up to date with your address, contact number, email address etc.
If their tax notices are ignored, the system will simply think you are ignoring them and continually load you with penalties, fines and more notices.
KEEP HMRC UP TO DATE!