Pension Payments Deferred thru Employer Error

[Guest atraveler]

My mother unfortunately has failed to received certain survivor benefits due her after the death of her husband. After we noticed this "oversight" the employer made a lump-sum payment to her of about $70,000. According to the IRS we can account for this using the special rules for 10-year averaging (she qualifies). However this would result in a tax due of about $9,000, whereas if she had received the survivor benefits payments on a timely bases (monthly) she would have had no tax liability (i.e., her income would fall below the minimum). Somehow this does not seem reasonable. Is there any provision in which we could "recast" her income into prior years due to "reasonable error?"

- Andy