The following is from a site with details of the U.S. Constitution.
Click on - The U.S. Constitution Online
Section 8 - Powers of Congress (Article I, Section 8)
The Congress shall have Power To lay and collect Taxes, Duties, Imposts and Excises, to pay the Debts and provide for the common Defense and general Welfare of the United States; but all Duties, Imposts and Excises shall be uniform throughout the United States;
Amendment XVI - Income taxes authorized. (Ratified 2/3/13)
The Congress shall have power to lay and collect taxes on incomes, from whatever source derived, without apportionment among the several States, and without regard to any census or enumeration.

Are you filing with the correct form?
Form 2555 is the required form under subtitle A (income tax) according to the OMB
Treasury Decision 2313 (Approved, March 30, effective January 1, 1916) clarifies that the Form 1040 individual income tax return is appropriate for any person acting as a fiduciary for a nonresident alien and receiving interest and/or dividends from the stock of domestic (US) corporations on behalf of that alien.

The following is directly from the 1040 Instructions, and links mentioned.
Click on - 2005 Inst 1040 Instructions for Form 1040 and Schedules - pdf file, long down load.
[These are instructions only, not regulations]
Page 12: Filing Requirements
Do You Have to File? Use Chart A, B, or C to see if you must file a return.
TIP Even if you do not otherwise have to file a return, you should file one to get a refund of any Federal income tax withheld.
Chart A--For Most People ** Gross income means all income you received in the form of money, goods, property, and services that is not exempt from tax...
Page 13: Chart B--For Children and Other Dependents Earned income includes wages, tips, and taxable scholarship and fellowship grants. Gross income is the total of your unearned and earned income.
Chart C--Other Situations When You Must File
You must file a return if any of the four conditions below apply for 2001.
Page 58: Amended Return
File Form 1040X to change a return you already filed. Generally Form 1040X must be filed within 3 years after the date the original return was filed, or 2 years after the date the tax was paid, whichever is later.
Page 59: Frivolous Return.
In addition to any other penalties, the law imposes a penalty of $500 for filing a frivolous return. A frivolous return is one that does not contain information needed to figure the correct tax or shows a substantially incorrect tax because you take a frivolous position or desire to delay or interfere with the tax laws. This includes altering or striking out the preprinted language above the space where you sign.
(This note is not included, but info you should have. Note: the Supreme Court has ruled that zeros on a return are information that is relavant on a return. Irwin Schiff's zero returns are legal)
Page 75: Disclosure, Privacy Act, and Paperwork Reduction Act Notice
     The IRS Restructuring and Reform Act of 1998, the Privacy Act of 1974, and Paperwork Reduction Act of 1980 require that when we ask you for information we must first tell you our legal right to ask for the information, why we are asking for it, and how it will be used. We must also tell you what could happen if we do not receive it and whether your response is voluntary, required to obtain a benefit, or mandatory under the law.
     This notice applies to all papers you file with us, including this tax return. It also applies to any questions we need to ask you so we can complete, correct, or process your return; figure your tax; and collect tax, interest, or penalties.
     Our legal right to ask for information is Internal Revenue Code sections 6001, 6011(a), and 6012(a) and their regulations. They say that you must file a return or statement with us for any tax you are liable for. Your response is mandatory under these sections. Code section 6109(a) requires that you provide your social security number or individual taxpayer identification number on what you file.This is so we know who you are, and can process your return and other papers. You must fill in all the parts of that tax form that apply to you.
     You are not required to provide the information requested on a form that is subject to the Paperwork Reduction Act unless the form displays a valid OMB control number.

IRS Restructuring and Reform Act of 1998 (President signed it on July 22, 1998)
[These sections may be needed when dealing with the IRS, so get familiar with them.]
RRA § 3401,

The following is directly from the IRS code.
Internal Revenue Code (Environmental Code, Title 26, Subtitle A-K)
CHAPTER 61 - INFORMATION AND RETURNS (Subtitle F, Chapter 61)
[These sections specifically depicted from the instuctions are listed according to the order specified.]
§ 6001. Notice or regulations requiring records, statements, and special returns (Chapter 61, Subchapter A, Part I)
Every person liable for any tax imposed by this title, or for the collection thereof, shall keep such records, render such statements, make such returns, and comply with such rules and regulations as the Secretary may from time to time prescribe. Whenever in the judgment of the Secretary it is necessary, he may require any person, by notice served upon such person or by regulations, to make such returns, render such statements, or keep such records, as the Secretary deems sufficient to show whether or not such person is liable for tax under this title. The only records which an employer shall be required to keep under this section in connection with charged tips shall be charge receipts, records necessary to comply with section 6053(c), and copies of statements furnished by employees under section 6053(a).
§ 6011(a). General requirement of return, statement, or list. (Chapter 61, Subchapter A, Part II, Subpart A)
(a) General rule
When required by regulations prescribed by the Secretary any person made liable for any tax imposed by this title, or with respect to the collection thereof, shall make a return or statement according to the forms and regulations prescribed by the Secretary . Every person required to make a return or statement shall include therein the information required by such forms or regulations.
§ 6012(a). Persons required to make returns of income (Chapter 61, Subchapter A, Part II, Subpart B)
(a) General rule
Returns with respect to income taxes under subtitle A shall be made by the following:
§ 6109(a). Identifying numbers (Chapter 61, Subchapter B)
(a) Supplying of identifying numbers
When required by regulations prescribed by the Secretary
§ 6053(c). Reporting of tips (Chapter 61, Subchapter A, Part III, Subpart C)
(c) Reporting requirements relating to certain large food or beverage establishments
(1) Report to Secretary
In the case of a large food or beverage establishment, each employer shall report to the Secretary, at such time and manner as the Secretary may prescribe by regulation, the following information with respect to each calendar year:
§ 6053(a). Reporting of tips (Chapter 61, Subchapter A, Part III, Subpart C)
(a) Reports by employees
Every employee who, in the course of his employment by an employer, receives in any calendar month tips which are wages (as defined in section 3121(a) or section 3401(a)) or which are compensation (as defined in section 3231(e)) shall report all such tips in one or more written statements furnished to his employer on or before the 10th day following such month. Such statements shall be furnished by the employee under such regulations, at such other times before such 10th day, and in such form and manner, as may be prescribed by the Secretary.
[Example: As a waitress you perform services for a customer, so these tips specified in section 6053 are not included; but if you serve your employer then only those tips would be included. If your employer tells you everything to do for a customer without a customer speaking to you directly will only these tips be included!]
§ 3121(a). Definitions (Subtitle C, Chapter 21, Subchapter C)
(a) Wages
For purposes of this chapter [21 - Federal Insurance Contributions Act], the term "wages" means all remuneration for employment, including the cash value of all remuneration (including benefits) paid in any medium other than cash; except that such term shall not include -
§ 3401(a). Definitions(Subtitle C, Chapter 24)
(a) Wages
For purposes of this chapter [24 - Collection of Income Tax at Source on Wages], the term "wages" means all remuneration (other than fees paid to a public official) for services performed by an employee for his employer, including the cash value of all remuneration (including benefits) paid in any medium other than cash; except that such term shall not include remuneration paid -
§ 3231(e). Definitions(Subtitle C, Chapter 22, Subchapter D)
(e) Compensation
For purposes of this chapter [22 - Railroad Retirement Tax Act] -
(1) The term "compensation" means any form of money remuneration paid to an individual for services rendered as an employee to one or more employers. Such term does not include

[These sections that are listed are according to the info you need in support of dealing with the IRS.]
(Authority from the Secretary)
§ 6201(a). Assessment authority (Subtitle F, Chapter 63, Subchapter A)
(a) Authority of Secretary.
The Secretary is authorized and required to make the inquiries, determinations, and assessments of all taxes (including interest, additional amounts, additions to the tax, and assessable penalties) imposed by this title, or accruing under any former internal revenue law, which have not been duly paid by stamp at the time and in the manner provided by law. Such authority shall extend to and include the following:
(1) Taxes shown on return.
The Secretary shall assess all taxes determined by the taxpayer or by the Secretary as to which returns or lists are made under this title.
§ 6203. Method of assessment (Subtitle F, Chapter 63, Subchapter A)
The assessment shall be made by recording the liability of the taxpayer in the office of the Secretary in accordance with rules or regulations prescribed by the Secretary. Upon request of the taxpayer, the Secretary shall furnish the taxpayer a copy of the record of the assessment.
§ 6212(a)(d). Notice of deficiency (Subtitle F, Chapter 63, Subchapter B)
(a) In general.
If the Secretary determines that there is a deficiency in respect of any tax imposed by subtitles A or B or chapter 41, 42, 43, or 44 he is authorized to send notice of such deficiency to the taxpayer by certified mail or registered mail.
(d) Authority to rescind notice of deficiency with taxpayer's consent.
The Secretary may, with the consent of the taxpayer, rescind any notice of deficiency mailed to the taxpayer. Any notice so rescinded shall not be treated as a notice of deficiency for purposes of subsection (c)(1) (relating to further deficiency letters restricted), section 6213(a) (relating to restrictions applicable to deficiencies; petition to Tax Court), and section 6512(a) (relating to limitations in case of petition to Tax Court), and the taxpayer shall have no right to file a petition with the Tax Court based on such notice. Nothing in this subsection shall affect any suspension of the running of any period of limitations during any period during which the rescinded notice was outstanding.
§ 6213(a). Restrictions applicable to deficiencies; petition to Tax Court (Subtitle F, Chapter 63, Subchapter B)
§ 6512(a). Limitations in case of petition to Tax Court (Subtitle F, Chapter 66, Subchapter B)
§ 7602. Examination of books and witnesses (Subtitle F, Chapter 78, Subchapter A)
(b) Purpose may include inquiry into offense The purposes for which the Secretary may take any action described in paragraph (1), (2), or (3) of subsection (a) include the purpose of inquiring into any offense connected with the administration or enforcement of the internal revenue laws.
§ 7651(2A). Administration and collection of taxes in possessions (Subtitle F, Chapter 78, Subchapter D)
(2) Tax imposed in possession - In the case of any tax which is imposed by this title in any possession of the United States -
(A) Internal revenue collections - Such tax shall be collected under the direction of the Secretary, and shall be paid into the Treasury of the United States as internal revenue collections; and
§ 6320(a). Notice and opportunity for hearing upon filing of notice of lien (Subtitle F, Chapter 64, Subchapter C, Part I)
(a) Requirement of notice.
(1) In general.
The Secretary shall notify in writing the person described in section 6321 of the filing of a notice of lien under section 6323.
§ 6321. Lien for taxes (Subtitle F, Chapter 64, Subchapter C, Part II)
§ 6323. Validity and priority against certain persons (Subtitle F, Chapter 64, Subchapter C, Part II)
§ 6330(a). Notice and opportunity for hearing before levy (Subtitle F, Chapter 64, Subchapter D, Part I)
(a) Requirement of notice before levy.
(1) In general.
No levy may be made on any property or right to property of any person unless the Secretary has notified such person in writing of their right to a hearing under this section before such levy is made.
§ 6331(a)(b). Levy and distraint (Subtitle F, Chapter 64, Subchapter D, Part II)
(a) Authority of Secretary.
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).
§ 6334. Property exempt from levy (Subtitle F, Chapter 64, Subchapter D, Part II)
§ 3401(d). Definitions (Subtitle C, Chapter 24)
(d) Employer For purposes of this chapter, the term “employer” means the person for whom an individual performs or performed any service, of whatever nature, as the employee of such person, except that—
(1) if the person for whom the individual performs or performed the services does not have control of the payment of the wages for such services, the term “employer” (except for purposes of subsection (a)) means the person having control of the payment of such wages, and
(2) in the case of a person paying wages on behalf of a nonresident alien individual, foreign partnership, or foreign corporation, not engaged in trade or business within the United States, the term “employer” (except for purposes of subsection (a)) means such person.

The following is information that may be bought up in dealing with the IRS.
RRA § 3401 - Due Process in IRS Collection Actions
C. Changes: Notice of Federal Tax Lien (NFTL). RRA § 3401 adds a new I.R.C. § 6320 to provide that the Service must notify in writing the taxpayer against whom a NFTL has been filed.