Stock sales and asset sales fall into this category, with the pressure on buyers to uncover any potential employee benefit issues prior to the conclusion of the deal while they can still be addressed with the seller.

Stock sales have more potential to cause problems for the buyer, with "any design problems or compliance issues that the seller has with respect to its employee benefit plans becom[ing] the buyer's problems and issues at closing."

Asset sales give a buyer more control over the employee benefit issues that it assumes, and the buyer can attempt to minimize benefit issues by refusing to adopt any of the seller's benefit plans, the report says. That will narrow the scope of due diligence and the representations in the purchase agreement, but there could still be issues of successor liability.

2. Multiemployer plans. Multiemployer plans can make a buyer think twice about completing a deal, since the buyer will be tied into a collectively bargained qualified retirement plan to which more than one unrelated employer is required to contribute. And that can leave them open to withdrawal liability—either because of their own withdrawal, or because of others' withdrawals down the line.

3. ESOPs. Then there are employee stock ownership plans, which add complexity and costs that can cause problems in an acquisition. Among those problems are the necessity to preserve voting rights on shares held in an ESOP, which is a fiduciary duty. The employer and the ESOP trustee may prefer to pass through voting rights to shift the fiduciary duty to the ESOP participants.

4. Defined benefit plans. Defined benefit plans not only require employers to satisfy minimum funding standards, but could also require an infusion of cash if the employer chooses to terminate the plan. In addition, participants must be offered the opportunity to have benefits paid in the form of an annuity—and the cost of that likely won't be known until the annuities are purchased and benefits distributed to participants. That can take months after the formal plan termination date.

5. Successor liability: Last but not least is that successor liability mentioned earlier, which can have not only to do with retirement plans, but also executive retirement plans and retiree medical plans.

According to the report, "Generally, a buyer of the assets of a business does not assume the seller's employee benefit liabilities unless expressly stated in the purchase agreement. However, there is a line of case law in which courts have imposed liability on a buyer of assets for the seller's employee benefit liabilities. This is commonly referred to as the 'successor liability' doctrine." And that means that "the existence of continuity of the business after closing and the buyer's knowledge of the liability prior to closing will sometimes lead a court to hold the buyer liable for the seller's unpaid benefit liabilities."

Thus, the report warns, buyers should "proceed with caution when dealing with these situations."