How do I determine the way statutory payments are processed for different TRUs?

Summary:

On one of our TRUs, the statutory payments are not balancing as we would expect, when we are trying to journal it. This is the first time there have been these stat payments earned on this payroll/TRU. The same payments work on other TRUs with no issues.

I don't think this is a system issue, more a processing issue. Because of this, I need to work out where in the system the stat payments derive from for different TRUs and then how to fix it, so they balance correctly going forward.

I appreciate this might be somewhat vague but any pointers on where to find where the stat payments are created would be helpful.