The trial, which could lead to a jail sentence of up to five years for former Bankia chairman Rato, is a politically and socially-charged case since more than 300,000 retail shareholders lost their life savings in the capital hike.
The court is set to pore over Bankia's near-collapse and subsequent bailout that was one of the focal points of the European debt crisis. Rato, a former economy minister who served as IMF head in 2004-7, is already serving a 4-1/2 year prison term on a separate embezzlement sentence.
Rato, who resigned from Bankia in 2012, has always denied any wrongdoing and attributed the accounting changes to writedowns against future losses when the bank changed management rather than to actual losses on his watch.
Bankia declined to comment and Rato's lawyer was not immediately available for comment.
Reuters was unable to contact the other board members or their lawyers for comment.
Less than a year after Bankia raised 3.1 billion euros ($3.5 billion) in the July 2011 share offering, the bank restated its 309 million euro profit for 2011 to a 3 billion euro loss.
The Spanish government had to quickly nationalise the lender via a 22.5 billion euro bailout. With the banking system at the time reeling under pressure from the European debt crisis, the move ultimately forced Spain to resort to a 41 billion euro European financial aid package in 2012.
More than 30 executives of the now state-owned lender, Bankia's parent company Banco Financiero de Ahorros (BFA) and auditors Deloitte are expected to testify before the court, probably starting in early January after opening technical proceedings, said a source familiar with the legal process.
Deloitte declined to comment.
A small Spanish political party, UPyD, forced Spain's High Court more than six years ago to open a criminal investigation into whether Rato and other Bankia executives were guilty of fraud, price-fixing or falsifying accounts.
In January 2016, the Supreme Court confirmed that the financial accounts used in Bankia's IPO did not accurately reflect the bank's situation.
Prosecutors are seeking charges of fraud against four former board members of Bankia, including Rato, for whom they are demanding a five-year-jail sentence.
Bankia was formed in 2010 from the merger of seven unlisted savings banks.
The 2011 accounts were reformulated by Bankia's current team, headed by chairman Jose Ignacio Goirigolzarri. Bankia has already paid back almost 1.9 billion euros in compensation to minority shareholders.