Adds new paragraph (4) to subsection (d) of section 382 creating an exception preserving net operating loss carryforwards that arose in start-up period taxable years (defining 'start-up period taxable year' and 'net start-up loss'), setting allocation rules for multiple trades or businesses, specifying a continuity-of-business requirement, excluding application in certain Title 11/insolvency cases and to disallowed interest, and including a transition rule for trades/businesses beginning on or before January 31, 2026.

Redesignates existing subsection (e) as subsection (f) and inserts a new subsection (e) establishing an exception for unused general business credits that arose in start-up period taxable years (a 'start-up excess credit'), defines applicable terms by reference to section 382(d)(4)(B), applies rules similar to specified rules in section 382(d)(4), and includes a transition rule excluding trades/businesses that began on or before January 31, 2026.

Replaces and reorganizes section 195 to expand and simplify the deduction rules for start-up and organizational expenditures, redesignate subsections, add a definition for organizational expenditures and apply rules to certain disregarded entities, and specify entity-level election rules for partnerships and S corporations.