In a variety of contexts, taxpayers can file tax elections that dictate their tax treatment. After filing or not filing a given tax election, a taxpayer might later feel regret. Perhaps the taxpayer lacks adequate information about the election's existence or tax effects at the time the taxpayer makes (or fails to make) the election. Later, the taxpayer acquires additional tax law information revealing that an alternative election would have produced more favorable tax results. Alternatively, the taxpayer may make an election because it will produce favorable tax consequences if the taxpayer's transactions or behavior play out the way the taxpayer predicts. When the taxpayer's predictions prove to be inaccurate, the taxpayer wishes she had made a different election. A taxpayer who learns that an earlier election was, in retrospect, ill-advised might attempt to benefit from her newly acquired knowledge by retroactively filing a new election. Tax law's limitations on the use of hindsight determine whether the taxpayer will succeed. Existing literature lacks an analysis focused on the questions of when taxpayers can and should be able to act on their regrets by using hindsight. The first aim of this Article is to undertake a thorough examination of restrictions on (and allowed uses of) hindsight when making tax elections. By focusing on the use of hindsight and analyzing the relevant rules collectively, this Article demonstrates that the tax law's approach to the use of hindsight is far from consistent. The second aim of this Article is to suggest and analyze underlying policy goals that motivate restrictions on the use of hindsight. An examination of the underlying policy goals brings to light some features of existing law that are useful and others that merit revision. The use of hindsight affects tax revenue collection and the fairness of the tax system and thus is a topic of significance at any time. In addition, certain recent legislative changes relate to restrictions on the use of hindsight when making tax elections
