Mauritius is already one of the 10 largest investors in Mozambique, having invested $3 bn in the past five years. And on a 1-3 February visit to the country, President Filipe Nyusi encouraged more Mauritius investment. (AIM En 1,3 Feb)
Mauritius is a major African tax haven. "Mauritius has an international reputation built around extremely low taxes - a flat corporate tax rate of 15% and an effective rate as low as 0 to 3% for offshore companies - as well as high levels of financial secrecy," according to an article in journal Foreign Policy (18 October 2018) Meanwhile Mozambique has a a very low tax rate for Mauritius registered companies. Mauritius has been accused by civil society groups of draining public resources from poorer countries by allowing multinational investors to shift their profits there, enabling them to pay much less than their fair share of taxes in the countries where they actually operate, Foreign Policy notes.
The secrecy could work the other way, and allow Mozambicans to use illegal money (such as from bribes and the $2 bn secret debt) to set up companies in Mauritius and then bring the money to Mozambique totally legally.