Saudi Aramco, the top global oil exporter, is preparing to give investors first-ever peak at its accounts, unfolding the financial details of the world’s most closely-held companies ahead of a planned initial public offering (IPO) in 2018.

The company, which has been the main revenue earner for the kingdom for the past eight decades, is overhauling accounts to be able to publish its 2017 financial year in an industry-friendly format, according to London-based Financial Times, which cited people close to the company. Aramco also plans to reveal backdated accounts in this format for its 2015 and 2016 financial years to investors, which could be released as soon as next year, the report added.

Riyadh aims to list less than 5 per cent of Saudi Aramco, which according to the kingdom’s Deputy Crown Prince Mohammed bin Salman al-Saud, could value the firm at more than $2tn, making it the world’s largest listed company. Its valuation will surpass Apple, currently in top spot, which has a market capitalisation of more than $600bn.

Saudi Arabia, the Opec’s biggest oil producer relies heavily on sale of crude for revenues, which accounted for more than 80 per cent of its income in 2015. The kingdom which is facing an estimated $87bn of deficit this year has embarked upon an austerity campaign, which has seen remodelling of state subsidy structure, reduction of public wage bill including 20 per cent cut in minister’s salaries and slashing perks of government sector employees. The country has borrowed from local and international markets to plug the widening budget deficit drew down on its foreign reserves to meet expenses.

Prince Mohammed in June announced the National Transformation Plan which lays emphasis on part privatising some of the state assets and developing alternative revenues streams such as income from investing activites. Aramco is at the heart of the government’s economic diversification plan and Prince Mohammed at the time had said that investors would get access to Aramco’s financials as part of its listing process. Saudi Aramco, which has been pumping record crude for the last three months has never issued financial statements.

The government is mulling floating Aramco’s shares on Saudi Stock Exchange (Tadawul) and a still undetermined international bourse. JPMorgan Chase has the lead advisory role on the transaction.

Analysts estimate that Saudi Aramco generated higher revenues than Apple and Microsoft combined in 2014, before the worst of the oil crash that began in the middle of that year, according to the news report.

But the company’s performance has long been deemed a black box by the energy industry and its advisers, due to its entanglement with the Saudi state.

As well as financing the majority of government spending, Saudi Aramco is a big domestic employer, constructing schools, hospitals and sport stadiums.

This makes disclosure of the company’s core energy activities a complex task. Saudi Aramco is said to be trying to organise its reporting along the lines of multinational oil companies such as BP and ExxonMobil, which disclose revenue and earnings generated from crude production, refining and petrochemicals.

Saudi Aramco declined to comment to the Financial Times on its IPO plans.

Khalid al-Falih, the Saudi energy minister, said in June that the state would retain control over the country’s crude output targets and production capacity, suggesting Saudi Aramco would not have the decisive say on these matters.