Aim: To investigate the influence of gestational age (GA) on the association between completion of the final examination after 10–11 years of basic education and education, financial independence and income in early adulthood. Methods: A nationwide register-based study including individuals born in Denmark between 1990 and 1992. Completion of the examination was evaluated at age 18 and education, financial independence and income at age 28. Results: Of 165 683 individuals included, 15.7%, 10.8% and 5.5% had low educational level, were not financially independent and had low income. For those who completed the examination odds ratio (OR) ranged from 1.03 at GA = 32–36 weeks to 1.25 at ≤27 weeks for low education, from 1.10 to 0.91 for not being financial independent and from 1.06 to 1.48 for low income. For those who did not complete the examination, OR increased from 7.55 at ≥37 weeks to 15.03 at ≤27 weeks for low education and from 4.68 to 15.31 for not being financial independent. For low income, OR was 2.57 and independent of GA. Conclusion: For individuals who completed the examination, the odds of poor socioeconomic outcomes were independent of GA. Individuals who did not complete the examination had increased odds of poor socioeconomic outcomes, particularly as GA decreased.