Pulte Homes has become the latest builder to adopt a "poison pill" provision to preserve potential tax benefits from an unintended change of ownership.

The company announced March 5 that it has adopted a shareholder rights plan that would be triggered if any shareholder acquires ownership of 4.9% or more of the company's outstanding securities without the approval of Pulte's board of directors.

In that event, the company's stock would be significantly diluted. In connection with the plan, Pulte declared a dividend of one preferred share purchase right for each of its common shares outstanding as of March 16, 2009.

"Pulte Homes' ability to use its net operating losses and other tax benefits would be substantially limited by Section 382 if an 'ownership change' occurred," the company said in the announcement of the plan. And an ownership change, as defined by the tax code, could happen without the builder even knowing it through typical stock-selling traffic. By definition, it would occur if half the owners of 5% or more of the company's stock changes over three years.

Pulte stressed that the provision isn't an anti-takeover measure. And some stockholders will be exempt, including those who hold 4.9% of the company's stock, unless they buy more shares.

"In addition, at its discretion, the board of directors may exempt certain persons whose acquisition of securities is determined by the board not to jeopardize Pulte's deferred tax assets and may also exempt certain transactions."

Stock movement at Beazer Homes USA and Standard Pacific triggered unintended changes of ownership last year that limited the tax refunds they can receive from the massive losses they have logged in recent years.

In addition to Pulte, K. Hovnanian Homes, M/I Homes, Centex, and Meritage Homes Corp. have all approved similar provisions that would trigger stock dilution if an ownership change is imminent.