Company: PTY
Filing Date: 2025-03-03
Form Type: POS EX
Source: 0001193125-25-042988
Chunk: 0

Company: PIMCO CORPORATE & INCOME OPPORTUNITY FUND
Filing Date: 2025-03-03
Form: POS EX
Chunk 0
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As filed with the Securities and Exchange Commission on February 28, 2025 1933 Act File No. 333-274752 1940 Act File No. 811-21238 UNITED STATES SECURITIES AND EXCHANGE COMMISSION Washington, D.C. 20549 Form N-2 (Check appropriate box or boxes)

| REGISTRATION STATEMENT             |     | ☒ |
| UNDER                              |     |   |
| THE SECURITIES ACT OF 1933         |     |   |
| Pre-EffectiveAmendment No.         |     | ☐ |
| Post-Effective Amendment No.1      |     | ☒ |
| And                                |     |   |
| REGISTRATION STATEMENT             |     |   |
| UNDER                              |     |   |
| THE INVESTMENT COMPANY ACT OF 1940 |     | ☒ |
| Amendment No.20                    |     | ☒ |

PIMCO CORPORATE & INCOME OPPORTUNITY FUND (Exact Name of Registrant as Specified in Charter) 1633 Broadway New York, New York 10019 (Address of Principal Executive Offices) (Number, Street, City, State, Zip Code) ( 888) 877-4626 (Registrant’s Telephone Number, including Area Code) Ryan G. Leshaw c/o Pacific Investment Management Company LLC 650 Newport Center Drive Newport Beach, California 92660 (Name and Address (Number, Street, City, State, Zip Code) of Agent for Service) Copies of Communications to:

| David C. Sullivan, Esq.               
 Adam M. Schlichtmann, Esq.            
 Ropes & Gray LLP                      
 Prudential Tower, 800 Boylston Street 
 Boston, Massachusetts 02199           |     | Douglas P. Dick, Esq.  
 Adam T. Teufel, Esq.   
 Dechert LLP            
 1900 K Street, N.W.    
 Washington, D.C. 20006 |

Approximate Date of Proposed Public Offering: This post-effective amendment is being filed pursuant to Rule 462(d) under the Securities Act and will be effective upon filing.

| ☐Check box if the only securities being registered on this Form are being offered pursuant to dividend or interest reinvestment plans.                                                                                                                                  |     | ☐Check box if this Form is a registration statement pursuant to General Instruction B or a post-effective amendment thereto that will become effective upon filing with the Commission pursuant to Rule 462