According to the National Accountability Bureau (NAB), Zardari, who is also the Pakistan Peoples Party (PPP) co-chairman, had acquired Karachi-based real estate firm Park Lane Estate Company (Pvt) Ltd illegally through a front man in 1989.
In 2009, Zardari and Bilawal became shareholders of the company.
The NAB claimed that billions of rupees were transferred to the company through fake bank accounts. The company also took loans of billions of rupees from banks using the political clout of Zardari, it claimed.
The 63-year-old husband of the country's first woman prime minister Benazir Bhutto was arrested by NAB officials in the Park Lane case on July 1. He was already in NAB's custody since June 10 after the Islamabad High Court dismissed his pre-arrest bail petition in the fake accounts case.
According to the NAB, Zardari is being investigated for his alleged involvement in extending loans and other misappropriation by Parthenon Private Limited, Park Lane Estate Private Limited and others.
Zardari's sister Faryal Talpur was also arrested in the fake account case.
The 11th president of Pakistan from 2008 to 2013 has denied any link with the fake accounts. He has said the allegation was part of a vilification campaign by Imran Khan-led ruling Pakistan Tehreek-e-Insaf (PTI) party to malign the Opposition leaders.