The answer depends on what the tax rate is.
999
1998
999 + 9999999999 + 9999999999 + 8888888 = 20,008,889,885
999 + 781 = 1780
999 + 99 = 1098
399 + 999 + 4999 + 899 + 999 + 599 + 899 + 1499 + 4499 + 100 = 15891
999
1998
There are two formats of Tax Identification Number (TIN) in the Philippines and they are 999-999-999-999V for vendors and customers that are subject to VAT and 999-999-999-999N for those that are not subject to VAT.
999
999 + 9999999999 + 9999999999 + 8888888 = 20,008,889,885
999 999
999 + 99 = 1098
999 + 781 = 1780
999 + 36 = 1035
999 + 12,345 is 13,344.
333 + 999 = 1332