C-Corp Form 1120 Reconciliation from Mixed Sources When reconciling corporate tax filings from multiple conflicting sources (invoices, bank deposits, expense sheets), establish a single authoritative source—typically the cash-basis expense sheet prepared from actual bank activity. Map each expense line item to specific Form 1120 schedules (J, K, L, M-1). Identify critical missing data gaps (beginning-of-year balances, capital structure, bank balances) and determine whether the return can file without them. Use this workflow: (1) declare source of truth, (2) line-by-line mapping to form, (3) g…