-----BEGIN PRIVACY-ENHANCED MESSAGE----- Proc-Type: 2001,MIC-CLEAR Originator-Name: webmaster@www.sec.gov Originator-Key-Asymmetric: MFgwCgYEVQgBAQICAf8DSgAwRwJAW2sNKK9AVtBzYZmr6aGjlWyK3XmZv3dTINen TWSM7vrzLADbmYQaionwg5sDW3P6oaM5D3tdezXMm7z1T+B+twIDAQAB MIC-Info: RSA-MD5,RSA, TwIbyyu8RlY0r2cFmUOONPwBPMdprEcCrooS239tEyRQwEQACH1CuPZ4DSVNJhFm JPIqN9UWHjnr5j2hN3/XrA== 0001047469-06-008211.txt : 20060609 0001047469-06-008211.hdr.sgml : 20060609 20060608213752 ACCESSION NUMBER: 0001047469-06-008211 CONFORMED SUBMISSION TYPE: FWP PUBLIC DOCUMENT COUNT: 1 FILED AS OF DATE: 20060609 DATE AS OF CHANGE: 20060608 SUBJECT COMPANY: COMPANY DATA: COMPANY CONFORMED NAME: CENTRAL ILLINOIS PUBLIC SERVICE CO CENTRAL INDEX KEY: 0000018654 STANDARD INDUSTRIAL CLASSIFICATION: ELECTRIC & OTHER SERVICES COMBINED [4931] IRS NUMBER: 370211380 STATE OF INCORPORATION: IL FISCAL YEAR END: 1231 FILING VALUES: FORM TYPE: FWP SEC ACT: 1934 Act SEC FILE NUMBER: 333-59438 FILM NUMBER: 06895348 BUSINESS ADDRESS: STREET 1: 607 E ADAMS ST CITY: SPRINGFIELD STATE: IL ZIP: 62739 BUSINESS PHONE: 217-523-3600 MAIL ADDRESS: STREET 1: CENTRAL ILLINOIS PUBLIC SERVICE CO STREET 2: 607 E ADAMS ST CITY: SPRINGFIELD STATE: IL ZIP: 62739 FILED BY: COMPANY DATA: COMPANY CONFORMED NAME: CENTRAL ILLINOIS PUBLIC SERVICE CO CENTRAL INDEX KEY: 0000018654 STANDARD INDUSTRIAL CLASSIFICATION: ELECTRIC & OTHER SERVICES COMBINED [4931] IRS NUMBER: 370211380 STATE OF INCORPORATION: IL FISCAL YEAR END: 1231 FILING VALUES: FORM TYPE: FWP BUSINESS ADDRESS: STREET 1: 607 E ADAMS ST CITY: SPRINGFIELD STATE: IL ZIP: 62739 BUSINESS PHONE: 217-523-3600 MAIL ADDRESS: STREET 1: CENTRAL ILLINOIS PUBLIC SERVICE CO STREET 2: 607 E ADAMS ST CITY: SPRINGFIELD STATE: IL ZIP: 62739 FWP 1 a2171136zfwp.htm FWP
QuickLinks -- Click here to rapidly navigate through this document

Filed Pursuant to Rule 433
Registration No. 333-59438
June 8th, 2006


PRICING TERM SHEET

Issuer:   Central Illinois Public Service Company d/b/a AmerenCIPS

Ratings:
 
A3/A-

Issue:
 
Senior Secured Notes due 2036

Offering Size:
 
$61,500,000

Coupon:
 
6.700% per annum, payable semi-annually on each June 15th and December 15th, commencing December 15th, 2006

Trade Date:
 
June 8th, 2006

Settlement Date:
 
June 14th, 2006

Maturity:
 
June 15th, 2036

Treasury Benchmark:
 
5.375% due February 15th, 2031

US Treasury Spot:
 
103-07

US Treasury Yield:
 
5.143%

Spread to Treasury:
 
160 basis points

Re-offer Yield:
 
6.743%

Price to Public (Issue Price):
 
99.449%

Gross Proceeds:
 
$61,161,135

Underwriting Discount:
 
0.875%

Net Proceeds:
 
$60,623,010

Optional Redemption:
 
Make Whole call, at any time at a discount rate of Treasury plus 30 bps

Minimum Denomination:
 
$1,000 × $1,000

Bookrunners:
 
Citigroup, Goldman, Sachs & Co.

        The issuer has filed a registration statement (including a prospectus) with the SEC for the offering to which this communication relates. Before you invest, you should read the prospectus in that registration statement and other documents the issuer has filed with the SEC for more complete information about the issuer and this offering. You may get these documents for free by visiting EDGAR on the SEC Web site at www.sec.gov. Alternatively, the issuer, any underwriter or any dealer participating in the offering will arrange to send you the prospectus if you request it by calling Goldman, Sachs & Co. toll-free at 1-866-471-2526 or Citigroup Global Markets Inc. toll-free at 1-877-858-5407.



QuickLinks

PRICING TERM SHEET
 -----END PRIVACY-ENHANCED MESSAGE-----