Congress will soon have access to a treasure trove of information about President Trump’s taxes. It just needs to ask New York.

A new state law, which sailed through the New York Legislature and now awaits the signature of Gov. Andrew Cuomo, would allow the heads of Congress’s tax-writing committees to request a public official’s state tax returns to aid the committees in a “legitimate” task.

The law does not single out President Trump, but it will permit the House Ways and Means Committee — which has so far been stymied by the Treasury Department in its investigation of Mr. Trump’s taxes — to obtain evidence of his tax reporting practices and the results of I.R.S. audits. When Mr. Cuomo signs the legislation — which he has said he will do — Richard Neal, the chair of the House Ways and Means Committee, need only ask Albany for the records.

Mr. Neal never should have needed New York’s help here. A 1924 federal statute provides that the Treasury secretary “shall” furnish any individual’s tax records upon written request from the Ways and Means chairman or his Senate counterpart. Invoking that law last month, Mr. Neal requested six years of Mr. Trump’s tax filings to assist his panel’s inquiry into the I.R.S.’s audits of the president. Nevertheless, Steven Mnuchin, the Treasury secretary, denied that request as well as a subsequent congressional subpoena for the president’s returns.