Edgar Filing: SOUTHWESTERN ENERGY CO

UNITED STATES
SECURITIES AND EXCHANGE COMMISSION
Washington, D.C. 20549

FORM 12b-25

NOTIFICATION OF LATE FILING

(Check one): o Form 10-K o Form 20-F x Form 11-K o Form 10-Q o Form 10-D o Form N-SAR o Form N-CSR

For Period Ended: December 31, 2005

o Transition Report on Form 10-K

o Transition Report on Form 20-F

o Transition Report on Form 11-K

o Transition Report on Form 10-Q

o Transition Report on Form N-SAR

For the Transition Period Ended:

1-08246
Commission File Number

Read Instruction (on back page) Before Preparing Form. Please Print or Type.

Nothing in this form shall be construed to imply that the Commission has verified any information contained herein.

If the notification relates to a portion of the filing checked above, identify the Item(s) to which the notification relates:

PART I - REGISTRANT INFORMATION

Southwestern Energy Company 401(k) Savings Plan

Full Name of Registrant

Former Name if Applicable

2350 N. Sam Houston Parkway E., Suite 300

Address of Principal Executive Office (Street and Number)

Houston, Texas 77032

City, State and Zip Code

PART II - RULES 12b-25(b) AND (c)

If the subject report could not be filed without unreasonable effort or expense and the registrant seeks relief pursuant to Rule 12b-25(b), the following should be completed. (Check box if appropriate)

(a) The reason described in reasonable detail in Part III of this form could not be eliminated without unreasonable effort or expense (b) The subject annual report, semi-annual report, transition report on Form 10-K, Form 20-F, Form 11-K, Form N-SAR or Form N-CSR, or portion thereof, will be filed on or before the fifteenth calendar day following the prescribed due date; or the subject quarterly report or transition report on Form 10-Q or subject distribution report on Form 10-D, or portion thereof, will be filed on or before the fifth calendar day following the prescribed due date; and (c) The accountant's statement or other exhibit required by Rule 12b-25(c) has been attached if applicable.

PART III - NARRATIVE

State below in reasonable detail why Forms 10-K, 20-F, 11-K, 10-Q, 10-D, N-SAR, N-CSR, or the transition report or portion thereof, could not be filed within the prescribed time period.

The Annual Report on the Form 11-K for the year ended December 31, 2005 (the "2005 Form 11-K") for the Southwestern Energy Company 401(k) Savings Plan (the "Registrant") cannot be filed within the prescribed time period because the registrant was unable to obtain the necessary information form the Registrant's record keeper. Consequently, the Registrant was unable to finalize its financial statements in a timely manner and will be unable to file the 2005 Form 11-K for the plan without unreasonable effort and expense. The Registrant expects to file the Form 11-K on or before the fifteenth calendar day following the prescribed due date.

SEC 1344 (03-05) Persons who are to respond to the collection of information contained in this form are not required to respond unless the form displays a currently valid OMB control number.

(Attach extra Sheets if Needed)
PART IV - OTHER INFORMATION

(1) Name and telephone number of person to contact in regard to this notification

Timothy J. O'Donnell 479 582-8427

(Name)

(Area Code) (Telephone Number)

(2) Have all other periodic reports required under Section 13 or 15(d) of the Securities Exchange Act of 1934 or Section 30 of the Investment Company Act of 1940 during the preceding 12 months or for such shorter period that the registrant was required to file such report(s) been filed? If answer is no, identify report(s). Yes x No o

(3) Is it anticipated that any significant change in results of operations from the corresponding period for the last fiscal year will be reflected by the earnings statements to be included in the subject report or portion thereof? Yes x No o

If so, attach an explanation of the anticipated change, both narratively and quantitatively, and, if appropriate, state the reasons why a reasonable estimate of the results cannot be made.

The net increase in net assets available for benefits expected to be reported by the Registrant for the year ended December 31, 2005 is approximately $10.9 million. The net increase in net assets available for benefits for the year ended December 31, 2004 was approximately $5.4 million. This increase between the comparative periods is due principally to increased appreciation in the fair value of plan investments and the receipt of rollover contributions.

Southwestern Energy Company 401(k) Savings Plan

(Name of Registrant as Specified in Charter)

has caused this notification to be signed on its behalf by the undersigned hereunto duly authorized.

Date

June 30, 2006 By /s/ Timothy J. O'Donnell

Vice President - Human Resources

INSTRUCTION: The form may be signed by an executive officer of the registrant or by any other duly authorized representative. The name and title of the person signing the form shall be typed or printed beneath the signature. If the statement is signed on behalf of the registrant by an authorized representative (other than an executive officer), evidence of the representative's authority to sign on behalf of the registrant shall be filed with the form.

ATTENTION
Intentional misstatements or omissions of fact constitute Federal Criminal Violations (See 18 U.S.C. 1001).