D.C. Tried to Change Its Tax Rules. Congress Said No.

Most taxpayers don’t think about the unique legal status of Washington, D.C., until Congress reminds them.

In February 2026, Congress passed a resolution blocking the District of Columbia from moving forward with legislation that would have decoupled its tax system from certain federal corporate alternative minimum tax (CAMT) guidance. The move underscores a reality that makes D.C. different from every state in the country: Congress retains the authority to overturn District laws.

Here’s what happened — and why it matters.

What D.C. Tried to Do

The District had passed legislation aimed at decoupling from federal guidance related to the Corporate Alternative Minimum Tax (CAMT), a provision originally created under the Inflation Reduction Act and later clarified through federal guidance.

In simplified terms, D.C. sought to prevent certain federal CAMT interpretations from automatically flowing through to its local tax code. This kind of “decoupling” is common among states — they often choose whether to conform to federal tax changes or maintain separate rules.

However, because D.C. is not a state, its legislative actions are subject to congressional review.

What Congress Did

Both chambers of Congress passed a joint resolution disapproving the District’s decoupling legislation, effectively preventing it from taking effect.

Under the District of Columbia Home Rule Act, Congress has the authority to review and nullify local D.C. legislation within a specified window.

The Senate’s resolution means D.C. must continue to conform to federal CAMT guidance rather than implementing its proposed divergence.

Why This Matters for D.C. Businesses

The Corporate Alternative Minimum Tax applies primarily to large corporations with average annual financial statement income exceeding $1 billion.

For affected D.C.-based corporations:

• The District will continue conforming to federal CAMT interpretations.
  
  
• Any planning based on anticipated D.C. decoupling must be revisited.
  
  
• Financial statement and state-level projections may need adjustment.

While the direct impact is limited to larger corporate taxpayers, the broader implications involve tax conformity and predictability.

The Bigger Issue: D.C.’s Limited Tax Autonomy

What makes this story particularly notable isn’t just the tax mechanics — it’s the governance structure.

Unlike states, the District of Columbia does not have full fiscal autonomy. Congress retains constitutional authority over the District and can:

• Review and reject local legislation
  
  
• Modify or impose budget constraints
  
  
• Override tax changes

For D.C. lawmakers and residents, this creates a recurring tension between local governance and federal oversight.

In this case, Congress exercised its authority to maintain alignment between D.C. and federal corporate tax guidance.

What Should D.C. Taxpayers Do?

For most individual D.C. residents, this development will not directly affect personal tax returns.

For corporate taxpayers and tax departments in the District:

• Monitor updated guidance from D.C.’s Office of Tax and Revenue.
  
  
• Reassess projections tied to CAMT conformity.
  
  
• Confirm state and local modeling reflects continued federal alignment.

This is also a reminder that for D.C. taxpayers, tax law can shift not just through local council votes, but through congressional action.

Congress’s decision to block D.C.’s decoupling legislation reinforces a key reality: The District operates under a different tax governance structure than any state.

For large corporations subject to CAMT, conformity remains intact. For policymakers, the episode highlights ongoing debates about D.C.’s fiscal autonomy. For taxpayers, it’s a reminder that in Washington, tax policy can change at two levels of government, sometimes quite unexpectedly.