@Kostas_matak
There is no requirement to document property that you own. You’re only required to report income, which can include selling property for a profit.
in the case of property that you received as a gift, your cost basis is the same as the cost basis of the original giver. That means the price that your father paid for the property, plus the price for any permanent improvements that he made. If you don’t have this information, you may be able to get it from whatever town or county or provincial office keeps records of real estate transactions, that might have a record of when your father purchased the property.
if you sell the property, you are going to calculate capital gains based on the cost basis, the selling price, and other adjustments. This is recorded on form 8949 and schedule D. The IRS does not have to award any cost basis that you can’t prove with reliable records. If you guess or estimate the cost basis and are selected for audit, and can’t prove the basis that you claim, the IRS could assign a zero basis, and you would pay capital gains tax on the entire sales proceeds.
Here is a link to more information.
https://www.irs.gov/taxtopics/tc409
