Washington’s much-celebrated healthcare reform measure has apparently tripped an unexpected accounting consequence, causing major corporations to announce non-cash hits to earnings and prompting Congress to schedule a hearing.

Credit Suisse published a report predicting S&P 500 companies in total will take charges to their first-quarter earnings to reduce their deferred tax assets by $4.5 billion as a result of the Patient Protection and Affordable Care Act signed last week by President Obama. The report says the hit to earnings results from recognizing the effect of a tax increase in the future “and shoving it into current period results,” making it a non-cash charge.

While the healthcare reform measure levies some $400 billion in tax increases, the focus of the first-quarter hit to earnings is a reduction in a Medicare drug subsidy, the report says. Companies that currently receive a 28-percent subsidy from the government for providing prescription drug coverage to their Medicare-eligible retirees will face the higher taxes in 2013, but must report the expected impact of it immediately as a result of accounting rules.

AT&T has filed an 8-K with the Securities and Exchange Commission announcing plans to take a $1 billion non-cash charge to earnings because of the new bill. “As a result of this legislation, including the additional tax burden, AT&T will be evaluating prospective changes to the active and retiree health care benefits offered by the company,” the firm said. Caterpillar says it will take a charge of $100 million as a result of the legislation, and Deere & Co. says its charge will amount to $150 million.

The House Sub-committee on Oversight and Investigations has scheduled an April 21 hearing to investigate, inviting the CEOs of AT&T, Caterpillar, and Deere to testify. The committee also invited Verizon to testify based on an e-mail communication the committee believes Verizon issued to its employees advising them to brace for higher costs as a result of healthcare reform.

The sub-committee is troubled by the announcements. “The new law is designed to expand coverage and bring down costs, so your assertions are a matter of concern,” the sub-committee chairs wrote in inviting the companies to testify. “They also appear to conflict with independent analyses,” referring to projections from the Congressional Budget Office that companies that insure more than 50 employees would see a decrease of up to 3 percent in average premium costs per person by 2016.

A Caterpillar spokesman said the company is following guidance in Accounting Standards Codification under Topic 740: Income Taxes. PricewaterhouseCoopers issued an alert that says the first healthcare bill, along with the subsequent reconciliation bill, change the tax treatment related to a retiree drug subsidy that some companies receive. The health reform measure has the effect of reducing the employer’s deduction for the cost of retiree healthcare by the amount of the subsidy received.

As a result, says PwC, the deductible temporary difference and any related deferred tax asset on the employers’ balance sheet associated with the benefit plan will be reduced. “Under ASC 740, Income Taxes, the impact of the change in tax law should be immediately recognized in continuing operations in the income statement in the period that includes the enactment date,” PwC writes. “Immediate income statement recognition is required for the change in tax law even though some portion of the accumulated actuarial gains or losses related to the subsidy may be recorded in accumulated other comprehensive income in the balance sheet.”

Meanwhile medical device manufacturer Invacare Corp. also filed an 8-K suggesting higher prices may follow the new excise taxes it will face. “Once there is a clear understanding of what specific medical device products will be covered by the excise tax, the company will evaluate all of its available options to offset the impact of the proposed tax on the company’s financial results in 2013, including possible price increases on the relevant products,” the company wrote.