Designate a New Effective Date for a Post-effective Amendment Previously Filed Pursuant to Rule 485(a) (485bxt)

As filed with the Securities and Exchange Commission on February 8, 2013

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1933 Act Registration No. 333-174332 1940 Act Registration No. 811-22559 UNITED STATES SECURITIES AND EXCHANGE COMMISSION WASHINGTON, D.C. 20549 FORM N-1A REGISTRATION STATEMENT UNDER THE SECURITIES ACT OF 1933 [ ] Pre-Effective Amendment No. __ [ ] Post-Effective Amendment No. 19 [X] and/or REGISTRATION STATEMENT UNDER THE INVESTMENT COMPANY ACT OF 1940 [ ] Amendment No. 21 [X]

FIRST TRUST EXCHANGE-TRADED FUND IV
(Exact name of registrant as specified in charter)

120 East Liberty Drive, Suite 400
Wheaton, Illinois 60187
(Address of Principal Executive Offices) (Zip Code)

REGISTRANT'S TELEPHONE NUMBER, INCLUDING AREA CODE: [phone]

W. Scott Jardine, Esq., Secretary
First Trust Exchange-Traded Fund IV
First Trust Advisors L.P.
120 East Liberty Drive, Suite 400
Wheaton, Illinois 60187
(Name and Address of Agent for Service)

Copy to:
Eric F. Fess, Esq.
Chapman and Cutler LLP
111 West Monroe Street
Chicago, Illinois 60603

It is proposed that this filing will become effective (check appropriate box):

[ ] Immediately upon filing pursuant to paragraph (b)
[X] on March 11, 2013 pursuant to paragraph (b)
[ ] 60 days after filing pursuant to paragraph (a)(1)
[ ] on (date) pursuant to paragraph (a)(1)
[ ] 75 days after filing pursuant to paragraph (a)(2)
[ ] on (date) pursuant to paragraph (a)(2) of Rule 485

If appropriate, check the following box:

[X] this post-effective amendment designates a new effective date for a
previously filed post-effective amendment.

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CONTENTS OF POST-EFFECTIVE AMENDMENT NO. 19

This Post-Effective Amendment to the Registration Statement comprises the following papers and contents:

The Facing Sheet

The sole purpose of this filing is to delay the effectiveness of the Registrant's Post-Effective Amendment No. 8, as it relates to First Trust High Yield Fund, a series of the Registrant, until March 11, 2013. Parts A, B and C of the Registrant's Post-Effective Amendment No. 8 under the Securities Act of 1933 as it relates to First Trust High Yield Fund, filed on October 26, 2012, are incorporated by reference herein.

Signatures

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SIGNATURES

Pursuant to the requirements of the Securities Act of 1933 and the Investment Company Act of 1940, the Registrant certifies that it meets all of the requirements for effectiveness of this Registration Statement under rule 485(b) under the Securities Act and has duly caused this Registration Statement to be signed on its behalf by the undersigned, duly authorized, in the City of Wheaton, and State of Illinois, on the 8th day of February, 2013.

FIRST TRUST EXCHANGE-TRADED FUND IV

By: /s/ Mark R. Bradley --------------------------------------- Mark R. Bradley, President and Chief Executive Officer

Pursuant to the requirements of the Securities Act of 1933, this Registration Statement has been signed below by the following persons in the capacities and on the date indicated:

SIGNATURE TITLE DATE President and Chief February 8, 2013 /s/ Mark R. Bradley Executive Officer ----------------------------------- Mark R. Bradley Treasurer, Chief Financial Officer February 8, 2013 and Chief Accounting /s/ James M. Dykas Officer ----------------------------------- James M. Dykas ) James A. Bowen* Trustee ) ) ) Richard E. Erickson* Trustee ) ) ) Thomas R. Kadlec* Trustee ) BY: /s/ W. Scott Jardine ) -------------------- ) W. Scott Jardine Robert F. Keith* Trustee ) Attorney-In-Fact ) February 8, 2013 ) Niel B. Nielson* Trustee ) )

* Original powers of attorney authorizing James A. Bowen, W. Scott Jardine and Eric F. Fess, to execute Registrant's Registration Statement, and Amendments thereto, for each of the trustees of the Registrant on whose behalf this Registration Statement is filed, were previously executed, filed as an exhibit and are incorporated by reference herein.