What if a parent gifts real property to a child? My name was included in 25% of the title Of land when my dad was alive. When my dad died, I received the remaining 75% to the land. Now after 15 years, I sell the land. What is my cost basis to the land?

When the land is a gift from parent to child, the cost basis is what the PARENT paid for the land.

So for Cost basis 25% is the cost the parents paid And 75% is the fmv on date of inheritance?

https://www.law.cornell.edu/cfr/text/26/1.1014-6

Yes, that is correct