Why do reconciliation bottlenecks keep showing up at quarter-end even when month-end is “under control”?

Many finance teams feel like they have month-end close reasonably well managed, but quarter-end still becomes chaotic. The same reconciliation issues that seem manageable month to month suddenly become painful when volumes spike, adjustments pile up, and more stakeholders get involved.

What’s interesting is that even teams with mature close processes often find that quarter-end reconciliation breaks in different ways. The volume of exceptions increases, and timing differences become harder to unwind cleanly. Some teams I’ve spoken with use tools like Collatio Accounts Reconciliation software to keep routine matching stable, but quarter-end still exposes process and data issues that stay hidden during normal months.

For people in corporate finance or controllership roles, what changes at quarter-end that makes reconciliation so much harder?
Is it purely volume and deadlines, or are there structural differences in how data flows and approvals happen at quarter close?