If you are choosing to complete a multiyear or multimonth bank reconciliation, consider reconciling through the last month of your previous fiscal year, which for most companies would be your statement ending December 31, 20xx. Choosing a month to reconcile through that is two to three months in the past will make identifying the transactions that have not cleared the bank as of the month you are reconciling much easier.
From Laura Madeira’s QuickBooks 2010 Solutions Guide