What are one-time integration costs / cost-to-achieve, and how do you model them?

Cost-to-achieve means one-time cash costs required to realize synergies: severance, consulting, systems migration, plant consolidation, retention bonuses, and integration PMO costs. Model them separately from recurring EBITDA, usually below adjusted EBITDA and in cash flow. Phase them before or alongside synergy realization, tax-effect them if deductible, and include them in ROIC / value-creation analysis.