While the new tax law did not drastically simplify the individual tax code, millions of taxpayers could save a bit of time on their filings this year, by skipping itemized deductions and claiming the newly expanded standard deduction instead. (This assumes taxpayers know right away whether that’s the smartest course for them; if they don’t, they will need to take the time to add up itemized deductions anyway, and then compare with the standard deduction.)

But Democrats say there’s nothing in the draft form, by itself, that will simplify tax season for most Americans. The new form “only adds needless complexity and confusion,” said Representative Lloyd Doggett of Texas, the top Democrat on the Subcommittee on Tax Policy. “The longer Form 1040, which all taxpayers have used for decades, is being replaced with Republican mythology that will only complicate tax filing.”

The new form could make things more complicated for the I.R.S., which suffered a critical malfunction on the deadline day for filing tax returns this year. More than 90 percent of taxpayers currently file their taxes electronically, which is actually a boon to the agency, because paper returns are more difficult to process. If the new form reverses that trend and persuades more Americans to mail in their taxes, it could overwhelm an already stressed system.

An I.R.S. spokesman did not immediately respond to a request for comment on the draft 1040 form on Monday afternoon.

President Trump is a huge fan of the postcard idea, which he praised throughout the tax debate last fall and into tax season this spring. The new postcard form, though, sadly does not include a provision from Mr. Trump’s campaign plan to simplify the code: a one-page form that Americans facing no income tax liability could send to the Internal Revenue Service, which simply declared, “I win.”