Black's Law Dictionary, Sixth Edition, Page 474:
distraint: Seizure; the act of distraining or making a distress. The inchoate right and interest which a landlord has in the property of a tenant located on the demised premises. Upon a tenant's default, a landlord may in some jurisdictions distrain upon the tenant's property, generally by changing the locks and giving notice, and the landlord will then have a lien upon the goods. The priority of the lien will depend on local law. See Distress.
Flora v. United States, 362 U.S. 145, 1959:
“Our system of taxation is based upon voluntary assessment and payment, not upon distraint.”
TITLE 26 > Subtitle F > CHAPTER 64 > Subchapter D > PART II > Sec. 6331.
26 U.S.C. Sec. 6331. Levy and distraint
(a) Authority of Secretary
(a) If any person liable to pay any tax neglects or refuses to pay the same within 10 days after notice and demand, it shall be lawful for the Secretary to collect such tax (and such further sum as shall be sufficient to cover the expenses of the levy) by levy upon all property and rights to property (except such property as is exempt under section 6334) belonging to such person or on which there is a lien provided in this chapter for the payment of such tax. Levy may be made upon the accrued salary or wages of any officer, employee, or elected official, of the United States, the District of Columbia, or any agency or instrumentality of the United States or the District of Columbia, by serving a notice of levy on the employer (as defined in section 3401(d)) of such officer, employee, or elected official. If the Secretary makes a finding that the collection of such tax is in jeopardy, notice and demand for immediate payment of such tax may be made by the Secretary and, upon failure or refusal to pay such tax, collection thereof by levy shall be lawful without regard to the 10-day period provided in this section.
(b) Seizure and sale of property
The term ''levy'' as used in this title includes the power of distraint and seizure by any means. Except as otherwise provided in subsection (e), a levy shall extend only to property possessed and obligations existing at the time thereof. In any case in which the Secretary may levy upon property or rights to property, he may seize and sell such property or rights to property (whether real or personal, tangible or intangible).
Mortimer Caplin, Internal Revenue Audit Manual (1975)
"Our tax system is based on individual self-assessment and voluntary compliance".
Dwight E. Avis, former head of the Alcohol and Tobacco Tax Division
of the IRS, testifying before a House Ways and Means subcommittee in 1953
"Let me point this out now. Your income tax is 100 percent voluntary tax, and your liquor tax is 100 percent enforced tax. Now, the situation is as different as night and day. Consequently, your same rules just will not apply...".
Internal Revenue Manual, Chapter 1100, section 1111.1
"The purpose of the IRS is to collect the proper amount of tax revenues at the least cost to the public, and in a manner that warrants the highest degree of public confidence in our integrity, efficiency and fairness. To achieve that purpose, we will encourage and achieve the highest possible degree of voluntary compliance in accordance with the tax laws and regulations...".