MOP, Bk 3, v.4, 177
(a) For officers and employees receiving a salary of two thousand pesos or less per annum, a per diem of not to exceed two pesos;
(b) For those receiving more than two thousand pesos per annum, but not exceeding four thousand pesos per annum, a per diem of not to exceed three pesos;Any officer or employee whose compensation is fixed at other than the per annum basis may be given the rate of per diem authorized for that receiving compensation on the corresponding per-annum basis.
(c) For those receiving more than four thousand pesos per annum, but not exceeding six thousand pesos per annum, a per diem of not to exceed four pesos; and
(d) For those receiving more than six thousand pesos per annum, a per diem of not to exceed five pesos.