Reconciling every balance sheet account to external evidence, recording accruals and prepayments, checking stock and fixed assets, and producing statements that can be explained.
The reconciliation is the work. The statements themselves fall out of a ledger that has been reconciled.
Because it is the first time anyone has looked. Twelve months of small unexplained differences arrive at once, and each is a question to somebody who may not remember.
Monthly reconciliation converts one long, unpleasant exercise into twelve short ones, and the total time is markedly lower.
Reconcile monthly. Almost all of the close is reconciliation deferred.
Bank first as external evidence, then debtors and creditors, then stock and assets, then accruals.
Working papers explaining differences. Most of their time goes on establishing what happened.
Half an hour with your own data usually saves reading three of these. The guides will still be here afterwards.