Last week I wrote about the House version of the “Tax Cuts and Jobs Act,” an unbelievable fiscally irresponsible bill that adds at least $1.4 trillion to the deficit and could add as much as $1.7 trillion. Now, as the world turns, the Senate Finance Committee is marking up Chairman Orrin Hatch’s version of the bill. There are differences between the two, but both use timing tricks and other budget gimmicks to mask the true size of the deficits that these bills – and whatever comes out bringing the two together – will actually create. Saying that these tax bills understate their effects on the deficit is saying a lot – since they both clearly identify a $1.4 trillion increase in the deficit in the first 10 years. The budget gimmicks are designed to make it look like the changes in law cost less down the road. Keep in mind this is more than just salesmanship. It’s a requirement for the Senate, which is prohibited from increasing the deficit outside of the 10-year budget window in order to comply with its own budget reconciliation rules.

The Senate’s latest timing trick is the expiration of most of the individual tax breaks, which allows the deficit increases to take place within the 10-year budget window. (The main corporate provisions do not expire.) But history tells us that tax breaks rarely actually expire: Witness the near annual charade of “tax extenders” and the challenges Congress faced when it reached the “fiscal cliff.” As you may remember, in 2012, the tax cuts that George W. Bush signed after Congress passed them using the reconciliation process expired on Dec. 31, 2012, at the same time across-the-board spending cuts might have been imposed under the Budget Control Act. What happened? Congress did do some belt-tightening spending cuts, but almost all of the deficit reduction was negated by the permanent extension of most of the Bush “temporary” tax cuts.

Last week I also wrote about several provisions in the House bill that show no evidence of stimulating growth, as the bill purports to do, from the nuclear production tax credit to the contraction and then elimination of the estate tax. This week I want to focus on some of the provisions targeted exclusively at businesses.

Both bills announce a 20 percent flat rate for corporations, but the idea that this is truly a flat rate is disingenuous, since the bill does not eliminate many of the largest corporate deductions and credits, such as the Section 179 expensing deduction (actually expands it), and in many other cases simply modifies the existing provisions that the House eliminated outright. Current law is, in theory, a 35 percent flat rate for corporations, but the thicket of deductions and credits, along with clever gamesmanship, results in many large corporations playing effective tax rates close to zero. Even since the bill was released last week, the Senate has added back some corporate tax preferences because of pressure from affected industries. For example, the original bill proposed taxing stock options at the time they vest, when they become assets of the employees who hold them, rather than when they are sold. Tech start-ups complained, and the change was removed.

But as you have likely have seen in the news, one of big changes to the Senate tax bill since last week is that the current version repeals the individual mandate to purchase health insurance included in the Affordable Care Act. Doing this would yield $338 billion, according to the Congressional Budget Office. This will allow the Senate to add back in a few more breaks for families and individuals while not creating a deficit in the second 10-year window. This also is in response to the criticism that the bill caters to corporations at the expense of individuals. The savings come from less spending on government subsidies to help people buy insurance because fewer people would buy it, a fact that has doctors, hospitals and insurers up in arms.

Like the House bill, the Senate bill relies on the narrow, closed process of reconciliation to ensure that the majority need not consider the needs and wishes of the other political party. And like the House bill, the Senate version relies on magical thinking about growth as the only protection from massive increases to the deficit and debt.

We cannot afford that approach. Taxpayers deserve comprehensive tax reform. We know from experience that for the real thing to happen, responsibly, both parties need to roll up their legislative sleeves, debate and compromise. They need to come up with a package that eliminates special interest breaks to broaden the tax base and reduce rates while not adding the nation’s stratospheric $20 trillion debt. The last time the country got comprehensive tax reform was 30 years ago. It was a broader discussion that wasn’t rushed. That’s the playbook lawmakers should reuse.