We quantify the returns to higher education for degree disciplines, namely 'professional' degrees, Medicine/Dentistry, Law, Accountancy and Psychology, within the UK from 2007 to 2015. We estimate the returns to education in the form of employment and wage premia associated with each subject. Our analysis contributes to the existing literature on the topic of horizontal mismatch by estimating the wage premia in different occupational settings and identifying the penalty associated with horizontal mismatch in each field, and relative to all other graduates. We identify how wage premia vary between employment outcomes when individuals with professional degrees are employed inside, as opposed to outside, their professional sector. A distinct difference in mismatch penalties between male and female graduates was found. Male mismatch penalties are isolated to law graduates, while female mismatch penalties appear, and persist within all fields across the duration of a female graduate's career.