The 48-year-old, best known as bookmaker Des Barnes from 1990 until 1998, was hit with a petition after unpaid taxes.
Speaking to the Manchester Evening News, he explained that his decision to direct a film in Africa caused his financial hardship.
Middlemiss recalled: "It was partly-funded by myself but I didn't have the money to fund the rest of the film. Filming came to a grinding halt. It was nearly three-quarters of the way along the line.
"It has been a difficult time. Three-and-a-half years is a long time to fund myself without any income. I have had to get money from family and friends."
He elaborated: "They [the HMRC] applied for whatever they said I owed in back taxes. I disputed it and disputed it again.
"I was waiting for money to come in but I didn't have enough time so they petitioned for bankruptcy. I have petitioned for an annulment and that takes about six weeks to get done."
Middlemiss, who is no longer acting, also starred in ITV's gentle Sunday night drama Where the Heart Is between 2000 and 2006.
A tabloid newspaper recently claimed that Bev Callard - who portrayed Rovers Return landlady Liz McDonald in the soap - has also filed for bankruptcy.