Sponsoring a visa while being self employed

My fiance and I currently live abroad and are looking at the family reunification process for me to move to Belgium after we get married.


He is from Belgium and currently works remotely for a company based in Australia. He wants to continue to work there and the boss is willing to draft a new work contract that is in line with the labor and tax laws in Belgium. He has been with the company for 8 years and makes enough money to satisfy the income requirement. I recently heard that if the income comes from a foreign source it isn't allowed to be counted due to taxes. My fiance was saying that he just needs to get his paychecks and tax documents translated and adjusted to show what that is euros to show proof of a stable income. Has anyone gone through this process? We looked on the immigration and it just says that the appropriate tax information needs to be submitted but it mentions nothing about where the income has to come from.