SÃO PAULO—Brazil’s state-owned lender Caixa Economica Federal took its first formal step toward holding an initial public offering for its insurance subsidiary as part of an effort to help the government improve its fiscal situation.

Caixa filed a plan to sell shares with Brazil’s Securities and Exchange Commission, the CVM, though the lender didn’t unveil an exact timetable or the amount to be raised from the operation. The CVM must approve the plan before the sale can move forward.

BB Investimentos, UBS, Goldman Sachs, Bradesco BBI, Itau BBA, BTG Pactual, Bank of America Merrill Lynch, Brasil Plural, Citibank and Banco Santander were hired to coordinate the operation, according to the filing.

The Wall Street Journal reported in July that the bank plans to sell as much as 25% of the unit in an operation that could generate up to 11.25 billion reais ($3.2 billion), citing a person close to the plan who declined to be named. A bank spokeswoman declined to comment for this article. Caixa is fully controlled by Brazil’s federal government.

Banco do Brasil, the country’s largest government-run bank, two years ago raised 11.5 billion reais via the sale of shares in its pension and insurance unit, BB Seguridade. That sale, the largest IPO in the world in 2013, will likely serve as a reference for the IPO of Caixa’s insurance unit.