If you work for the post office, you're a civil servant. The Civil Rights movement focused on the notion that all American citizens were entitled to the same basic civil liberties.
There is also time limit to consider for sending the amended returns, and it is generally three years from the time you filed the returns or two years after the tax payment (whichever is later). If you plan to amend more than one tax return, you have to file separate 1040X for every one you want to change.
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.