C corporation returns — Form 1120 — are among the most technically demanding filings in the US tax system. The review process for a well-prepared 1120 is systematic and sequential. The following framework reflects the approach Marcken Solutions applies to 1120 review engagements.
The Review Framework
Start with the Trial Balance Tie-Out
Before reviewing any tax-specific items, confirm that the income and deduction totals on the return tie to the trial balance or adjusted financial statements. Any unexplained difference between book income and the starting point for the M-1 or M-3 reconciliation signals a problem that must be resolved before the review continues.
M-1 / M-3 Reconciliation
The book-to-tax reconciliation is the single most important document in the 1120 workpaper package. Every permanent and temporary difference should be identified, sourced, and documented. Common items requiring careful workpaper support: stock-based compensation deductions (Section 162(m) limitations), meals and entertainment disallowances, depreciation differences (MACRS vs book), deferred revenue recognition differences, and penalties.
State Apportionment
For corporations filing in multiple states, confirm that the apportionment factors — sales, payroll, property — are current and sourced to the correct underlying data. State apportionment factors change as the business changes. A factor that was correct three years ago may not be correct today. Review each state filing separately and confirm the factors before the return is finalised.
Depreciation and Section 168 Elections
Confirm that bonus depreciation and Section 179 elections are consistent with the entity’s prior-year positions and current-year strategy. For corporations with NOL carryforwards or alternative minimum tax considerations, bonus depreciation elections interact with other provisions in ways that require explicit modelling before the election is made.
NOL and Credit Carryforwards
Maintain a rollforward schedule of all NOL and credit carryforwards. The schedule should show opening balance, current-year additions or reductions, amounts utilised in the current year, and closing balance. The closing balance on the schedule must agree to the return.
The Partner Review Standard
A 1120 prepared to the standard described above should reach the partner review stage as a document that the reviewer can move through efficiently — not one that requires reconstruction. The workpaper trail holds up the computation; the reviewer’s role is to assess the judgements, not to rebuild the arithmetic.
Marcken Solutions provides 1120 preparation and review support for C corporation engagements. Contact us to discuss your filing requirements.