You close the file with everything reconciled. The bank matches, the dashboard is clean, you move on. The next morning you open Xero and the reconciliation is out, with a small difference that was not there yesterday or previously matched transactions that no longer line up. What makes this so frustrating is that nobody obviously edited anything, so the search is always some version of "why did my reconciliation change overnight." The answer is almost never random. Reconciliation in Xero reflects the current state of the ledger, not the state it was in when you closed the file, so if it changed, the transaction layer underneath it changed, and something new either entered the system or something old was altered after you finished.
Why a reconciled balance can move overnight
The most common cause is a delayed bank feed. A feed reconnects or updates overnight and brings in transactions dated earlier in the period, and those new entries sit unreconciled and shift the balance, even though you did nothing between closing the file and reopening it. Closely related is the duplicate problem: if you uploaded transactions by CSV during a feed disruption and the feed later catches up, it can reimport the same transactions, and duplicates appear that simply were not visible the day before. In both cases the change came from outside your actions entirely, which is exactly why it feels like the file broke on its own.
The other trigger is a backdated edit, and in a multi-person firm this is the one people forget. Someone unreconciles and redoes a transaction, changes an account code, or adjusts GST coding on a line dated earlier in the quarter, and because Xero recalculates against the current ledger, even a small change ripples into the running balance you thought was settled. Currency rounding on foreign transactions and changes to split allocations can move totals the same quiet way. None of these announce themselves on the reconciliation screen. They just change the number underneath it.
How to find what actually moved
If the reconciliation was balanced yesterday and is out today, do not go looking for your own mistake, because it usually is not one. Assume something was added, duplicated, or edited, and check in that order. Look at recent bank feed activity for transactions that came in with earlier dates. Review anything imported by CSV for duplicates against the caught-up feed. Then check for unreconcile-and-redo actions and any backdated journals posted into the period, which is where another team member's change will show up. Xero's account transactions list can be sorted by the date an entry was edited rather than the date of the transaction itself, which is the fastest way to surface what changed after you closed the file. Reconciliation does not break randomly. Once you find what moved, the balance falls back into place without guesswork.
