Dortmund finished second in the Bundesliga this season, 13 points behind Bayern who won the league for the eighth year running.
Dortmund are one of Europe's richest clubs and have equity capital of 355 million euros ($398 million).
However, due to the coronavirus pandemic they expect a deficit of 45 million euros for the 2019/20 season.
"What we are losing in income on all sides is dramatic," club CEO Hans-Joachim Watzke said Tuesday.
Dortmund lost millions in matchday revenue from the five home games they were forced to play behind closed doors.
The team is doing its part with the squad agreeing to take pay cuts until the end of the year.
The departure of Germany international Mario Goetze, whose contract included a yearly salary of 10 million euros, will ease the wage bill slightly.
Dortmund have signed Belgium defender Thomas Meunier from Paris Saint-Germain on a free transfer and England Under-17 midfielder Jude Bellingham is expected to join from Birmingham City.
Meunier will replace right-back Achraf Hakimi, whose two-year loan deal from Real Madrid has expired.
However, Meunier and Bellingham could be Dortmund's only new arrivals for the upcoming season.
Watzke said that as far as Dortmund are concerned, "the transfer market is dead. We're not planning any more transfers."
However, any clubs tempted to bid for Dortmund's teenage striker Erling Braut Haaland, who scored 16 goals in 18 games since his January arrival, or England winger Jadon Sancho have been warned.
"There won't be even a one cent discount due to the coronavirus," Watzke said at the weekend.