The House Freedom Caucus — a group of around 35 ultra-conservative House Republicans who can block their party's leadership on key legislation — is in the final stages of drafting its own tax plan, according to sources familiar with the process.

Freedom Caucus chairman Mark Meadows is expected to unveil his group's tax reform plan in the near future.

But sources familiar with the arrangements have leaked key details in the current draft of the Freedom Caucus plan. (These details haven't yet been formally discussed within the group and therefore aren't set in stone):

Slashes the corporate tax rate from 35% to 16%.

Doubles the standard deduction for individuals.

Abandons "revenue neutrality," the dogma that tax reform mustn't worsen currently projected deficits.

Instead of raising new sources of money to ensure their tax cuts don't add to deficits, the Freedom Caucus is planning to embrace a non-traditional idea to extend the budget window:

The idea, pushed by some conservatives, including Sen. Pat Toomey, is to change budget rules so that tax cuts that add to the deficit can last for 20 years or longer, rather than expiring after 10 years.

Pushes some form of "welfare reform" (of which I have obtained no details so far.)

Why this matters: It's a move designed to unsettle Republican leaders Paul Ryan and Mitch McConnell, who've been working behind closed doors to craft a tax plan with the White House. The group, known as the "Big Six" — the other members are tax-writing committee chairs Kevin Brady and Orrin Hatch, and administration officials Gary Cohn — has kept the details of their plan incredibly close to their vests.