I rented my property to my parents for a nominal (under market rate) rent. They ended up subletting it at market rate to someone else and keeping that rental income for themselves.
For my taxes, do I just report the nominal rental income my parents paid me or do I also have to report the income from the sublet my parents did?
Renting below market rate means you have a "not for profit" rental where the income & expenses do not get reported on a Sch E. Income goes on the Sch 1 and the expenses (limited to the income) on the Sch A.
Read all about it ... starting on page 16 https://www.irs.gov/pub/irs-pdf/p527.pdf
As @Bsch4477 said, you only report the income you actually received. Your parents are responsible for reporting any income they received from a sub-let.
Renting below market rate means you have a "not for profit" rental where the income & expenses do not get reported on a Sch E. Income goes on the Sch 1 and the expenses (limited to the income) on the Sch A.
Read all about it ... starting on page 16 https://www.irs.gov/pub/irs-pdf/p527.pdf