Is it legally obligatory to pay the annual subscription fee to the National Social Security Fund, knowing that the subscription period did not exceed nine months, and the internal regulations of the Fund stipulate that the full year's subscription must be paid if the individual exceeds March 15th before terminating the subscription?

For it to be permissible to participate in social security, it is a condition that it be based on cooperation, not exchange, and that its funds be invested in a Sharia-compliant manner. If these conditions are not met, then it is obligatory to repent from participating in it. If there was financial benefit from the participation, then what was taken must be returned, except for the amount paid, as Allah Almighty says: "And if you repent, you may have your principal – [thus] you do no wrong, nor are you wronged." However, if there was no benefit, then no contribution is required unless compelled.