Saudi Arabian Oil Company’s (Aramco) CEO, Amin Nasser said that the kingdom has promised it will reduce the overall tax rate paid by its national oil company to make its 2018 initial public offering more appealing to investors, Bloomberg reported. Aramco’s Nasser added that the company currently pays a 20% royalty on its revenue plus an 85% tax on income. Yet, he declined to say what tax rate the kingdom was considering.

This came as Saudi Arabian Energy Minister, Khalid al-Falih, confirmed that he still expected national oil giant Saudi Aramco to conduct a public offer of its shares in 2018, according to Gulf Business.

Officials have been working since early 2016 on complex details of the offer, including legal conditions, how to value Aramco’s assets, and on which exchanges its shares would be listed. Saudi Arabia is looking at markets including Hong Kong, London, New York and possibly even Canada as international venues for the sale. The kingdom will offer 5% of the world’s biggest oil producer as part of a plan by Deputy Crown Prince Mohammed bin Salman to set up a giant biggest sovereign wealth fund and help reduce the economy’s reliance on hydrocarbons.

Nasser said the kingdom was considering whether to do a double listing, with shares sold in the domestic market in Riyadh and a foreign exchange, or a triple-listing, with two foreign locations on top of the local bourse. Additionally, her said the Aramco IPO will include the so-called concession, which comprises the oil and gas reserves of the kingdom. Saudi Arabia sits on almost a fifth of the oil world’s reserves.