The District of Columbia has enacted permanent decoupling from several provisions of the federal One Big Beautiful Bill Act (B26-0661 / Act A26-0418), creating new compliance work for D.C. filers.
The decoupling forces federal-to-state add-backs on D.C. corporate franchise, individual income, and unincorporated business tax returns. Areas affected include research expenditures, interest expense near the section 163(j) limitation, pass-through entity-level taxes, and qualified production property.
For businesses and individuals filing in D.C., the practical effect is that federal and D.C. taxable income will now diverge on these items — permanently. Tax software and preparers need to reflect the D.C.-specific adjustments.
D.C. is not alone: several states have weighed conformity decisions since OBBBA's passage. If you file in multiple states, confirm each jurisdiction's conformity posture rather than assuming federal treatment carries over.