안녕하세요

영주권자의 경우, 해외로 출국하신 이후, 별도의 절차를 밟지 않으셔도, 장기간 해외체류를 하는 경우, 영주권을 포기한것으로 간주하게 됩니다. 또는 미국외에 체류하시면서 영주권을 반납하시려면, 영주권과 여권을 지참하고 현지의 미국영사관을 방문하셔서 I-407 서식을 제출하시면 되실듯 사료됩니다.

제 조언이 조금이라도 보탬이 되셨기를 바랍니다.

영주권의 포기에 의한 미국의 보호이탈의 경우에는 아래 절차를 따르시면 됩니다.
http://www.uscis.gov/i-407

Special Instructions
There are eight spaces for your A-number. If your A-number is only seven digits, place a zero (0) as the first digit.
If the lawful permanent resident is under 17 years old, the minor’s parents, custodial parents or legal guardians must sign and consent to submitting Form I-407.
If there is only one legal parent, that parent can sign Form I-407. However, that parent must submit proof:
1) Of having sole legal custody; or,
2) Showing that any other parent has either died or had his or her parental rights legally terminated.
A guardian must submit documentation showing that the guardian has legal custody or other authority to sign for the minor.

특히, 정식으로 국적이탈이 되는 경우 또는 영주권포기의 경우에는 해당자에 대해 국적이탈세를 부과합니다.

The Department of Homeland Security is required to provide the Internal Revenue Service (IRS) with the names of individuals who choose to abandon their LPR status. If you file this form with us, we will provide only your name and the filing date to the IRS. (Internal Revenue Code section 6039G(d)(3))

국적이탈세 (Expatriation Tax)에 대해 자세한 내용은 아래를 참조하세요.
http://www.irs.gov/Individuals/International-Taxpayers/Expatriation-Tax

26 U.S. Code § 877 - Expatriation to avoid tax
(a) Treatment of expatriates
(1) In general
Every nonresident alien individual to whom this section applies and who, within the 10-year period immediately preceding the close of the taxable year, lost United States citizenship shall be taxable for such taxable year in the manner provided in subsection (b) if the tax imposed pursuant to such subsection (after any reduction in such tax under the last sentence of such subsection) exceeds the tax which, without regard to this section, is imposed pursuant to section 871.
(2) Individuals subject to this section
This section shall apply to any individual if—
(A)the average annual net income tax (as defined in section 38(c)(1)) of such individual for the period of 5 taxable years ending before the date of the loss of United States citizenship is greater than $124,000,
(B)the net worth of the individual as of such date is $2,000,000 or more, or
(C)such individual fails to certify under penalty of perjury that he has met the requirements of this title for the 5 preceding taxable years or fails to submit such evidence of such compliance as the Secretary may require.
In the case of the loss of United States citizenship in any calendar year after 2004, such $124,000 amount shall be increased by an amount equal to such dollar amount multiplied by the cost-of-living adjustment determined under section 1(f)(3) for such calendar year by substituting “2003” for “1992” in subparagraph (B) thereof. Any increase under the preceding sentence shall be rounded to the nearest multiple of $1,000.
(b) Alternative tax
A nonresident alien individual described in subsection (a) shall be taxable for the taxable year as provided in section 1 or 55, except that—
(1)the gross income shall include only the gross income described in section 872(a) (as modified by subsection (d) of this section), and
(2)the deductions shall be allowed if and to the extent that they are connected with the gross income included under this section, except that the capital loss carryover provided by section 1212(b) shall not be allowed; and the proper allocation and apportionment of the deductions for this purpose shall be determined as provided under regulations prescribed by the Secretary.
For purposes of paragraph (2), the deductions allowed by section 873(b) shall be allowed; and the deduction (for losses not connected with the trade or business if incurred in transactions entered into for profit) allowed by section 165(c)(2) shall be allowed, but only if the profit, if such transaction had resulted in a profit, would be included in gross income under this section. The tax imposed solely by reason of this section shall be reduced (but not below zero) by the amount of any income, war profits, and excess profits taxes (within the meaning of section 903) paid to any foreign country or possession of the United States on any income of the taxpayer on which tax is imposed solely by reason of this section.