As filed with the Securities and Exchange Commission on December 4, 2017

File Nos. 333-126384

811-21781

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. 29	☒
and/or
REGISTRATION STATEMENT UNDER THE INVESTMENT COMPANY ACT OF 1940	☒
Amendment No. 31	☒

(Check appropriate box or boxes)

PIONEER SERIES TRUST IV

(Exact Name of Registrant as Specified in Charter)

60 State Street, Boston, Massachusetts 02109

(Address of Principal Executive Offices) (Zip Code)

Registrant’s Telephone Number, including Area Code: (617) 742-7825

Terrence J. Cullen, Amundi Pioneer Asset Management, Inc.

60 State Street, Boston, Massachusetts 02109

(Name and Address of Agent for Service)

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

☒ immediately upon filing pursuant to paragraph (b)

☐ on [date] 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:

☐ This post-effective amendment designates a new effective date for a previously filed post-effective amendment.

SIGNATURES

Pursuant to the requirements of the Securities Act of 1933, as amended, and the Investment Company Act of 1940, as amended, the Trust certifies that it meets all of the requirements for effectiveness of this Registration Statement pursuant to Rule 485(b) of the Securities Act of 1933. The Trust has duly caused this Post-Effective Amendment No. 29 to its Registration Statement to be signed on its behalf by the undersigned, duly authorized, in the City of Boston, and the Commonwealth of Massachusetts, on the 4th day of December, 2017.

PIONEER SERIES TRUST IV
By:	/s/ Lisa M. Jones
	Lisa M. Jones
	President

Pursuant to the requirements of the Securities Act of 1933, this Registration Statement has been signed below by the following persons in the capacities indicated below on December 4, 2017:

	Signature	Title
/s/ Lisa M. Jones Lisa M. Jones		President (Principal Executive Officer) and Trustee
Mark E. Bradley* Mark E. Bradley		Treasurer (Principal Financial and Accounting Officer)
David R. Bock* David R. Bock		Trustee
Benjamin M. Friedman* Benjamin M. Friedman		Trustee
Margaret B. W. Graham* Margaret B. W. Graham		Trustee
Lorraine H. Monchak* Lorraine H. Monchak		Trustee
Thomas J. Perna* Thomas J. Perna		Chairman of the Board and Trustee
Marguerite A. Piret* Marguerite A. Piret		Trustee
Fred J. Ricciardi* Fred J. Ricciardi		Trustee
Kenneth J. Taubes* Kenneth J. Taubes		Trustee
*By:	/s/ Lisa M. Jones
	Lisa M. Jones	Dated: December 4, 2017
	Attorney-in-fact

EXHIBIT INDEX

Exhibit No.	Description
EX-101.INS	XBRL Instance Document
EX-101.SCH	XBRL Taxonomy Extension Schema Document
EX-101.CAL	XBRL Taxonomy Extension Calculation Linkbase
EX-101.DEF	XBRL Taxonomy Extension Definition Linkbase
EX-101.LAB	XBRL Taxonomy Extension Labels Linkbase
EX-101.PRE	XBRL Taxonomy Extension Presentation Linkbase