In Belgium, many full time employees receive a salary bonus equivalent to one month’s salary, so it is called the 13th month salary, which is usually paid at the end of the year. Many employees also receive a vacation bonus, which is the equivalent of 92% of a month’s salary, and it is paid in the summer. To calculate your monthly salary from your gross salary, you should divide your annual salary by 13.92 to account for these two bonuses.