Total Salary by Division for the first of each month - OTBI

Summary:

I feel like maybe this is very obvious and I'm overlooking it. But here it goes:

We want a report that total salary for a given division on the first of each month. The idea is to be able to track how the total salary spend has changed over time in a given department. We're focusing on controlling our costs at the moment and this is important information for our business leaders to have.

All the reporting areas that I've looked at link salary to a date only when that salary has changed.

Content (required):

I want to be able to show total salary (for active and inactive employees) in a report that looks like the one below. I'm thinking the solution would sit somewhere in Payroll reporting because I'd like to capture the salary of terms that was previously paid out. But every date field I see is linked to salary or assignment changes. I want to be able to pull that salary into my report regardless of whether it changed.