Saudi Aramco is preparing to give investors unprecedented access to its accounts, lifting the lid on the world’s biggest oil producer ahead of a planned initial public offering in 2018. Saudi Arabia’s state-controlled oil company is busy overhauling its accounts so as to publish figures for its 2017 financial year in an industry-friendly format, said four people close to the company. It is also planning to show investors backdated accounts in this format for its 2015 and 2016 financial years, which could be released as soon as 2017. The kingdom’s influential deputy crown prince Mohammed bin Salman said in April that the planned listing of 5 per cent of Saudi Aramco could value the company at more than $2tn. This means it could become the world’s largest listed company:Apple, currently in top spot, has a market capitalisation of more than $600bn. The IPO is the cornerstone of prince Mohammed’s plan to reduce Saudi Arabia’s reliance on oil, by using proceeds from the flotation to diversify the country’s economy. This has become a priority after crude prices more than halved to about $50 a barrel in the past two years.