Migrating ledgers: tying opening balances to bank statements and uncleared items

When a business moves its books to a new provider, the opening ledger starts from the old provider's closing balance sheet. Each bank and card balance must match the bank's printed statement for the cutover date, adjusted for uncleared items such as an uncashed check. The author's rule is that the difference must be zero, and any unexplained gap signals a problem in the old books. The approach uses Decimal arithmetic in Python to avoid rounding errors that could mimic real discrepancies. If a gap cannot be explained, the advice is to trace back month by month to find where it first appeared rather than plugging it to equity.