New Delhi: State-owned Oil and Natural Gas Corporation (ONGC) will file papers for its much-delayed Rs 12,000 crore share sale with market regulator SEBI on Monday.

The follow-on public offer (FPO) is likely to open on September 20 and close on September 23, sources privy to the development said.

The board of ONGC had last week approved the red herring prospectus that will be filed with the Securities and Exchange Board of India (SEBI) on Monday.

The government plans to sell 5 per cent, or 427.77 million shares, through the FPO.

Sources said the RHP incorporates the financials of the company till the April-June quarter.

The FPO was originally planned in the 2010-11 fiscal, but the launch was later deferred to April 5 as the company did not have an adequate number of independent directors on its board to meet market regulator SEBI's listing norms.

It was then rescheduled for July 5, but was again deferred due to adverse market conditions.

The government had in January appointed Citigroup, Nomura Holdings, Bank of America Corp, HSBC Holdings, JM Financial Services and Morgan Stanley to manage ONGC's share sale.

After the FPO, the government's stake in ONGC will come down to 69.14 per cent from the current 74.14 per cent.   

The government's ad-hoc subsidy sharing mechanism has cast a shadow over ONGC's share sale during recent months.