Contractors shall send the invoice to the employer every month with 15 days of credit term, starting from the date of billing at the beginning of every month. The employer shall make the payment for the following month by cash transfer or by check. In case the contractor wishes to adjust the wage rate in accordance with the minimum rate of wages of the government. The contractor shall notify the employer for their consideration and approval in advance no later than 30 (thirty) days prior to the effective date in following month that such wage rates shall be applied. In case when the employer shall not agree with the adjusted rates, the contractor agrees and acknowledges that the employer has its right to terminate the contract immediately.