Mississippi Code Title 21. Municipalities § 21-29-321

For purposes of determining the “average monthly base salary and longevity pay” as provided in Sections 21-29-101 et seq., the wages to be considered shall be the average base salary and longevity pay which was received in consecutive pay periods immediately preceding retirement. This amount shall be the average of six (6) pay periods if the employee was paid monthly, or the equivalent if the pay periods are bi-weekly, semi-monthly or weekly. In addition, wages may include holiday pay and regularly scheduled overtime pay earned for services performed during the last six (6) months of employment, as certified by the employer.