ERR_CASH_FLOW on QuickBooks: Cash flow calculation error. Root cause: Cash flow statement contains error due to missing transactions, incorrect transaction categorization between operating, investing, financing activities, or formula error in calculation. Unreconciled bank transactions or timing differences between accrual and cash accounting can cause discrepancies. Step 1: Run cash flow statement and identify discrepancy. Go to Reports > Cash Flow Statement. Select reporting period. Run report and review sections: Operating Activities, Investing Activities, Financing Activities. Verify total cash inflows minus outflows equals change in cash balance. Compare ending cash balance to bank account balance. If mismatch, note the difference. Step 2: Reconcile cash balance to bank account. Go to Banking > Bank Reconciliation. Select the bank account. Run reconciliation for reporting period. Verify cleared balance matches bank statement ending balance. If mismatch, complete bank reconciliation first (clear all outstanding checks, deposits in transit). This is prerequisite for accurate cash flow. Step 3: Verify transaction categorization (operating vs investing vs financing). Review major transactions in cash flow. Operating: day-to-day business (sales, expenses, receivables, payables). Investing: asset purchases/sales, loan disbursements. Financing: debt, equity, dividends. If transaction in wrong category, cash flow totals will be wrong. Recategorize as needed. Step 4: Check for missing or duplicate transactions. Compare transactions on cash flow to general ledger. Verify all cash transactions appear. Look for duplicates (same transaction listed twice). Check for accrual entries that should not appear on cash flow (e.g., depreciation, accrued expenses that were not paid). Remove non-cash items. Step 5: Verify timing differences between accrual and cash. Cash flow uses cash basis (when money moves), not accrual basis (when transaction recorded). Example: invoice recorded in January but paid in February should appear in February cash flow. Check for timing mismatches. Verify accounts receivable and accounts payable changes are properly reflected as cash timing adjustments. Step 6: Recalculate cash flow and verify it balances. After corrections, re-run cash flow statement. Verify: Operating Cash Flow + Investing Cash Flow + Financing Cash Flow = Change in Cash. Verify ending cash balance matches bank account balance (after reconciliation). Only finalize period after cash flow balances and reconciles to bank.