If you've had tenants for five years you have to do a new one anyone. So, do one -start afresh . It's a new tenancy . Read the PRTB websiteso tyou better understand what i mean about the five eyar thing.
And why would you ask about whetehr tenants can have a copy of the application if thats the meaning of your question.?
If you haven't been registered with the PRTB - have you been claiming mortgage interest relief on your tax returns? If so you may be liable to repay this as you would not be entitled to claim that relief. Assuming of course you are registered with Revenue and otherwise tax compliant?