It's ok. I'm sure there were at least a few Trumpettes who voted early for a candidate Trump supports just because they knew a tax cut was coming before the election. The fact that Congress was not in session doesn't bother them in the least. If Donald said it, he can create an executive order to make it happen. The fact that the Constitution specifies that all revenue bills (additions or subtractions) must begin in the House of Representatives is of no consequence.
BTW, saying "he lied" is so harsh. Can't we just accept that the Donald is working with an alternative set of facts?