The Trump administration and congressional Republicans released their latest framework for tax reform earlier this week, finally pushing forward a key campaign plank on which the president rallied support during the run-up to the 2016 election. Lawmakers asserted that the move would provide a massive tax cut for Americans across the board. Yet even though the proposal provided some information about what negotiations will look like on Capitol Hill, it left out a key piece of information without which no taxpayer can accurately calculate what their tax liability would be under the new plan.

The key piece of the puzzle

What the proposal did include was the general layout of how taxes would look for individual taxpayers. Right now, there are seven income tax brackets, with rates ranging from 10% to 39.6% depending on income level. The new proposal reduces the number of brackets to three, and proponents argue that this move is in line with overall efforts to simplify the tax laws and make returns easier to prepare.

The proposal also says what the tax rates for those brackets will be. The lowest tax bracket will be 12%, sparking contention among those who note the apparent inconsistency between aiming tax cuts at ordinary Americans while raising the lowest available bracket. The middle rate of 25% is an amount that currently applies to upper-middle income earners, and the top rate of 35% mimics what Bush-era tax rates were before the legislation's sunset provisions took effect during the Obama administration.

Keyboard with blue tax button where the return key would be.

Image source: Getty Images.

What's missing is the taxable income level to which each tax bracket will apply. Without that key information, it's impossible to calculate what your taxes will be under the plan and compare them with your current tax liability.

Speculating about tax brackets

For guidance, it's helpful to look back at past discussions of tax reform. The original version of the administration's plan had the lowest tax bracket extend up to $37,500 of taxable income for singles and $75,000 for joint filers, which roughly matches up with what the 10% and 15% brackets currently cover. Because the 10% bracket currently includes only a small amount of income, those who earn the full $37,500 pay an effective tax rate that's closer to 14%. The two-percentage point cut would work out to about $750 under the plan.

For higher-income taxpayers, the proposed 25% bracket was seen going up to $112,500 for singles and $225,000 for joint filers. That covers the current 25% bracket, and for joint filers, it also includes most of the 28% bracket under the present tax system. With the proposed 35% bracket kicking in above those income levels, there were some taxpayers who would see bracket increases from current levels of 28% and 33%, while top earners would get an advantage by not having to pay the current 39.6% rate.

The failure of the proposal to include these numbers again shows that they're in flux and subject to negotiation. Until those figures are hammered out, members of the public won't be able to take informed positions on the legislation based on their own personal financial situations.

How other aspects of tax reform affect the numbers

The primary argument that lawmakers have made thus far about the increase of the lower bracket from 10% to 12% isn't that effective tax rates for many low-income workers will stay the same or go down. Rather, they point to a higher standard deduction, which will be roughly double the current amount. The proposal positions this as a "zero tax bracket" that should be considered part of the framework.

Yet other parts of the proposal will also affect individual tax bills. Personal exemptions aren't included in the reform package, which could result in higher overall taxable income for larger families even with a big standard deduction. An increase in the child tax credit could offset the loss of personal exemptions, but the amount of the boost isn't known. Elimination of many itemized deductions will tend to push more taxpayers to use the raised standard deduction, but that could be a net loss for those who claimed large itemized deductions, especially on the basis of the to-be-repealed deduction for state and local taxes.

Hurry up and wait

You'll find plenty of analysis of the Trump tax plan making broad generalizations about its impact. The current framework doesn't provide enough details to allow precise conclusions about what it will mean to you and other taxpayers. For that, lawmakers will have to fill in the blanks and figure out exactly which priorities it will emphasize in the final legislation.