Zack Nolan, Alexa Steinberg, and Sally James published the article "Mastering the Mailbox Rule So IRS Tax Forms Can Arrive on Time" to Bloomberg Tax.
"Tax practitioners often disagree on whether to use the US Postal Service or a private delivery service to deliver forms to the IRS. The two options are more equitable than some would think. [...]
Given the costly nature of a mistake in these contexts, individuals may get skittish when it comes to mailing tax documents. Practitioners and taxpayers generally fall into one of three camps when it comes to which delivery service is preferred: the US Postal Service; a private delivery service such as FedEx, UPS, or DHL; or no preference.
So, is the Postal Service better than a private delivery service in the eyes of Congress and, as a result, given preferential treatment? The answer may be more equitable than some would think."
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