The US tax authorities have generally let the parties to a transaction rescind it as long as the rescission occurs in the same tax year and the parties are restored to the same position
economically as if the transaction never occurred. 

The IRS may now be having second thoughts about this policy.

It is no longer issuing rulings to taxpayers who want to rescind transactions, and it committed in its annual business plan to issue new guidance by the end of June. However, that
guidance is now proving difficult to write. There is sympathy at the IRS for giving taxpayers the ability to fix mistakes by rescinding transactions, but a subjective test that requires an IRS agent to determine the intention of the parties is hard to administer. There is little sympathy for letting companies do retroactive tax planning.

The IRS associate chief counsel for passthroughs and special industries — the part of the IRS that deals with partnerships and the energy industry — issued five private rulings between 2002 and 2008 allowing rescissions. The associate chief counsel for corporate taxes issued at least 15 rulings between 2005 and 2011. The most recent was in June 2011.

The rescission doctrine dates to a 1940 US appeals court decision in Penn v. Roberston and a 1980 ruling, Revenue Ruling 80-58.