Discrepancies in deceased dad’s tax returns/ estate reporting

[Charlie Flowers]

my dad passed away a few months ago. I have been collecting rent on 2 legal units and 1 illegal unit in a 3 family home. The rent is paid in cash there are no leases. My dad and i resided in the first floor apartment. I’m in the process of submitting his will for probate where I Am the proposed executor and in doing so examined his tax returns for confirmation because no tenant has a lease. I noticed that the past two years my father underreported the rental income. He never reported any of the illegal units rent or the public assistance payments he was getting for my room. I don’t know whether to just repeat my father’s figures so as to settle his estate as quickly as possible and avoid any potential IRS mess + then remove the illegal unit/tenant once I am legally the owner and report properly as the new owner. Or I begin reporting properly now and open up my dad’s estate to a slew of lawsuits esp considering one of the units was illegally built. HELP!