Tax for Payroll in Philippines?

I have two questions that I am looking an answer for in Philippines:- (a.)Say for instance, an employee is being paid a salary and the pay period runs from the 20th of December to the 10th of January. What tax rates should apply? Will it be the current years or the next years? (b.)Say for instance, an employee was incorrectly paid in his/her last pay and we have to make adjustments for that employee in the next pay. The last pay ended on the 31st of December and the adjustments are to be made after the 1st of January, then what tax rates are applicable? I mean will it be the new tax rates that come into effect from the 01st of January or because the pay adjustments are being made for the last month’s pay, the tax rates applicable are from the last years? Your help would be greatly appreciated. Cheers Imran