How do you treat add-on acquisitions in a buy-and-build LBO model?

Model add-ons with purchase price, timing, financing mix, acquired EBITDA, synergies, integration costs, and incremental debt. Add acquired financials from closing date and update debt schedule. Track blended entry multiple, pro-forma leverage, and returns contribution. Add-ons can create value if acquired at lower multiples or if synergies are credible.