Recently, there has been a push for legislation to stop companies from benefitting from tax breaks as a result of "union busting" activities. Many employers spend money on "union avoidance" consultants, and the current laws allow companies to deduct anti-union consultant and advertising costs as necessary business expenses. However, a new bill has been proposed that would require these expenses to be reported to the IRS and make them non-tax deductible. Some experts say that this legislation is too broad though and will be challenging to implement.
See "In the US, potential tax code changes would prevent employers from including anti-union expenses in their tax deductions", Diego Areas Munhoz and Samantha Handler, Bloomberg Law, April 14, 2023