The BBC reports that the club also warned media revenues could fall by around £14m this year, partly because of its third-place finish in the Premiership last season.
Weaker performance on the pitch, as well its purchase of three new players - including Wayne Rooney - also dented the bottom line.
But it was not all bad news for the club as United said its operating profits rose 6 per cent on the year to £58.3m. The figure, which does not take into account the depreciating value of players, was up on last year's £55.1m.
United added that its decision to reinvest the proceeds of David Beckham's £25m transfer to Spain's Real Madrid had also hit profits for the year.
The group said the anticipated decline in media revenues partly reflected the Premiership's new three-year television contracts.
Media revenue from the Premier League is expected to fall by £8m while Uefa Champion's League cash will fall by £6m
The club's pre-tax profits were expected to dip in the wake of a poor performance last year, which saw United pick up just the FA Cup.
