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.
How many years back can you get a tax refund? The IRS Statute of Limitations allows you three years from the filing deadline to file your prior year return and claim your refund. For example, the last day to claim your tax refund for the 2013 tax year is April 15, 2017. This is because the deadline date was April 15, 2014. Keep in mind that they also have the same amount of time to audit you and up to ten years to collect any unpaid tax.