Manchester United will lose more than £20m in sponsorship income from Adidas if they fail to qualify for next year's Champions League.
First-quarter revenue - to 30 September - was down £3.4m (2.8%) to £120.2m, with matchday income down 32.3% to £16.8m. Profit was £6.2m.
The reduction in income is largely down to United playing three fewer home games than in the same period in 2015.
Debt has risen 18% to £337.7m, due to the fall in the pound against the dollar since the Brexit vote.
Executive director Ed Woodward said: "Our financial results for this quarter reflect the impact of our non-participation in the Uefa Champions League."
The club's commercial revenue rose 4.4% to £74.3m, with overall revenue for the year expected to be between £530m and £540m.