Contributions to fund the Social Security office to bill 2 times per year.The first time will be paid in 31 January every year. called "Annual contributions" 2 will be paid within 31 March every year. Called "the contributions of the reporting wages". Because of the contributions collected at the beginning of the year. Calculated from the wages that have been estimated in advance.Multiplied by the contribution rate During the year, which may be changed to increase or decrease wages So in February of each year.The employer has a duty to report the amount of wages paid to all employees, including last year To the social security office know. To be compared with the estimates of wages at the beginning of the year.If you pay less than the previous projection, it will be collected contributions increased in March. Unless wages are forecast higher real wages.The employer will receive a contribution paid over To summarize, it is The first collection will be collected in advance of the year. But the second is reconciliation from wages paid.Evaluated and compared to the total bill at the beginning of last year.If it's higher than return Less than they charge enough.