Like almost every president who preceded him, Lincoln's actions at the time were somewhat controversial. Some of his most controversial decisions might actually be considered now to be abuses of the Presidential power.
When you find that you need to amend a tax return, you need to make sure the statute of limitations on filing one hasn't run out. The statute of limitations, or time allowed for the action, on getting a refund from an amended tax return is three years.
The taxpayer can also file a refund claim for tax that he paid with the original tax return. Generally, under section 6511, the taxpayer is required to file a claim for refund within three years from the date the original return was filed or two years from the date the tax was paid, whichever is later.