def calculate_basic_salary(payroll_instance):
    basic_salary = 0.0
    total_bonuses = 0.0
    staff_bonuses = payroll_instance.bonus_instance.filter(recycle_bin=False)
    for bonus in staff_bonuses:
        total_bonuses += float(bonus.bonus_instance_value)
    basic_salary = float(payroll_instance.gross_salary) - \
        total_bonuses-float(payroll_instance.commissions_total)
    return str(basic_salary)