I am half black and half white. I identified as such on standardized tests by checking both “black” and “white”. Now as I am filling out my applications I am worried that I won’t be considered a “real” URM since for all the college knows I’m 1/16th or less. Will checking both boxes on my application disadvantage me vs. students who just check “black”? Is it considered lying if I only identify as black on my application?
If you identify as “black” you are not lying. Identifying as Black will indeed more advantageous for you, since “biracial” does not identify you as an URM, which you are. The definition of “Black” is usually " A person having origins in any of the black racial groups of Africa". That includes you as well.
Even if you have checked both Black and White or Biracial in the past, you can check Black from now on, and nobody will have an issue.