When budgeting headcount in the Philippines, what should be included beyond base salary to get the true cost per employee?

Base salary is just the starting point. Add employer-share SSS, PhilHealth, and Pag-IBIG, 13th month pay (roughly one extra month's basic salary a year), and any de minimis benefits you provide. Omni HR calculates all of these in the same payroll run, so the fully loaded cost per employee shows up in your reporting instead of a separate spreadsheet.