Washington (CNN) Small business owners may have a few more answers if they're hoping to take advantage of a major business tax break tucked in last year's new tax law.

The Treasury Department and Internal Revenue Service released on Wednesday long-awaited guidance on how US taxpayers can claim a 20% deduction on income for owners, partners and shareholders in so-called pass-through entities -- e.g. S-corps, LLCs, partnerships and sole proprietorships.

The proposed changes are part of a sweeping $1.5 trillion tax overhaul, which provided deep tax cuts for businesses, including setting a new corporate tax rate at 21%, down from 35%.

"The pass-through deduction is an important tax cut for small and mid-size businesses, reducing their effective tax rates to their lowest level since the 1930s," said Secretary Steven Mnuchin, in a statement. "Pass-through businesses play a critical role in our economy."

Owners of pass-through businesses, who pay taxes on their profits at the owner's individual tax rate, have wrestled with an additional dose of complexity about whether they qualify for the deduction.

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