United's debt, a source of fan opposition toward the owning Glazer family since their 2005 takeover, dropped to 359.7 million pounds ($570 million) by Sept. 30 from 436.9 million ($639 million) on June 30.
With the proceeds of its floatation, United paid off 62.6 million pounds ($100 million) of high-interest bonds.
The 134-year-old club's New York listing left the Glazer family, which also owns the NFL's Tampa Bay Buccaneers?, still with the biggest stake in United with almost total voting control. United shares were trading at $12.98 on Wednesday after opening at a discounted price of $14 in August.
The first-quarter results released Wednesday also showed that United recorded a profit of 20.5 million pounds ($33 million) compared with a loss of 5 million pounds ($8 million) a year earlier.
Commercial revenue is on course to reach at least 350 million pounds ($555 million) in the financial year after it grew by 24 percent to 43 million pounds ($68 million) in the first quarter.
Ten new sponsorship deals were struck in three months, including with General Motors whose Chevrolet brand will appear on United's shirts for seven years from the 2014-15 season under a $559 million agreement.
"Manchester United had a record first quarter driven by our commercial operation, which continues to experience extremely strong global revenue growth in new media and mobile, retail merchandising and sponsorship," vice chairman Ed Woodward said in a statement. "The team has also made a strong start to the 12/13 season."
After winning no trophies last season, Alex Ferguson's side currently tops the Premier League and its Champions League group, in part due to strengthening the squad.
Between July and September, United spent 29.5 million pounds ($47 million) on players, including midfielders Shinji Kagawa and Nick Powell, and the first of two payments to Arsenal for striker Robin van Persie.
Matchday revenue did rise by 2 million pounds ($3 million) to 19.6 million pounds ($31 million) in part due to payments for staging football matches at Old Trafford during the Olympics across July and August.
But United'us broadcast revenue dropped 37 percent year-on-year in the first quarter to 13.7 million pounds, ($22 million) due to there being only one Champions League game at Old Trafford compared with two in the period the previous year.