Manchester United is expected to become world football's biggest earners in the next 12 months.
Real Madrid topped Deloitte's Football Money League for the 11th consecutive year, generating 577m euros (£439m) in 2014-15.
Barcelona is second with 560.8m euros (£426.6m), with United third on 519.5m euros (£395.2m).
But Deloitte said there was a "strong possibility" United would overtake the La Liga sides in next year's edition.
Deloitte is a professional services firm, whose sports business group produces an annual table of the clubs with the highest revenues.