A s estate planners, we like to remember those plans that made our clients and their families richer, happier, or both. Although it is less pleasant to recall those cases when happy results were not achieved, it is probably more instructive to analyze why things go wrong. Many bad estate plans result from a failure in proper drafting or in dealing adequately with a tax requirement. A second lawyer who reviews a will or trust instrument may detect these “technical” mistakes. Fortunately, we can, by statute, deal retroactively with certain kinds of frequently recurring errors, such as an inadvertent general power of appointment, a violation of the common law Rule Against Perpetuities, or a failure to make a proper allocation of the GST transfer tax exemption.