The Treasury Department had a different standard for handling House Democrats’ request for President Donald Trump’s taxes, according to a letter from the department to Sen. Ron Wyden.

House Democrats have been locked in a battle with the Treasury Department over obtaining Trump’s personal and business tax returns. Treasury and Internal Revenue Service officials have denied or ignored requests and subpoenas for the documents.

Wyden said the letter shows that Treasury broke with tradition. Justin Sok, the senior adviser for Treasury’s Office of Legislative Affairs who signed the letter, defended the department’s response, noting the unusual nature of the request...