What is reconciliation?
The most boring word in payments, and the place money quietly disappears.
It is balancing a chequebook, if the chequebook covered ten thousand transactions a day, deducted a variable commission from each, and settled in batches whose composition you had to reconstruct.
Three systems, three versions of the same day. The difference between them is not an error. It is money.
Why three records exist and disagree
Your system records a sale. Your payment provider records a transaction. Your bank records a deposit. In an ideal world these agree perfectly.
They do not, routinely, for entirely mundane reasons. Settlements arrive net of fees, so the deposit never matches the sale. Refunds and chargebacks are deducted from later batches, so today's deposit reflects last week's returns. Transactions near a cutoff time land in a different day's batch. Currency conversion introduces rounding.
None of these are errors. All of them create differences that must be explained rather than ignored.
What breaks when nobody reconciles
Revenue is recognised that never arrived. Failed payments are treated as successful and goods are shipped for free. Duplicate charges to customers go unnoticed until they complain. Fee overcharges by providers are never detected, because nobody is checking the arithmetic on thousands of small deductions.
That last one is worth sitting with. Provider fee calculations are complex, tiered, and occasionally wrong. The businesses that reconcile properly find discrepancies. The ones that do not, do not find them, which is not the same as their absence.
Nobody has ever been promoted for reconciling well. Several people have been removed for not doing it.
Where you meet it
If you run any business taking payments, in the gap between your dashboard and your bank statement. If you do not, in the fact that your duplicate charge eventually got noticed by somebody.