Company: TEM
Filing Date: 2025-08-08
Form Type: S-8 POS
Source: 0001193125-25-176040
Chunk: 0

Company: Tempus AI, Inc.
Filing Date: 2025-08-08
Form: S-8 POS
Chunk 0
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As filed with the Securities and Exchange Commission on August 8, 2025 Registration No. 333-280270 Registration No. 333-285174 UNITED STATES SECURITIES AND EXCHANGE COMMISSION Washington, D.C. 20549 Post-Effective Amendment No. 1 to Form S-8Registration Statement File No. 333-280270 Post-EffectiveAmendment No. 1 to Form S-8Registration Statement File No. 333-285174 UNDER THE SECURITIES ACT OF 1933 Tempus AI, Inc. (Exact name of registrant as specified in its charter)

| Nevada                                   |     |         47-4903308 |
| (State or other jurisdiction of          
 incorporation or organization)           |     |   -I.R.S. Employer 
 Identification No. |
| 600 West Chicago Avenue, Suite 510       
 Chicago, Illinois                        |     |              60654 |
| (Address of Principal Executive Offices) |     |          -Zip Code |

Tempus AI, Inc. 2024 Equity Incentive Plan (Full titles of the plans) Eric Lefkofsky Chief Executive Officer, Founder and Chairman Tempus AI, Inc. 600 West Chicago Avenue, Suite 510 Chicago, Illinois 60654 (800) 976-5448(Name, address, including zip code, and telephone number, including area code, of agent for service) Copies to: Christina T. Roupas Courtney M.W. Tygesson Cooley LLP 110 North Wacker Drive Suite 4200 Chicago, IL 60606 Tel: (312) 881-6500 Indicate by check mark whether the registrant is a large accelerated filer, an accelerated filer, a non-acceleratedfiler, smaller reporting company, or an emerging growth company. See the definitions of “large accelerated filer,” “accelerated filer,” “smaller reporting company,” and “emerging growth company” in Rule 12b-2of the Exchange Act.

| Large Accelerated filer |     | ☐ |     | Accelerated filer         |     | ☐ |
| Non-accelerated filer   |     | ☒ |     | Smaller reporting company |     | ☐ |
|                         |     |   |     | Emerging growth company   |     | ☒ |

If an emerging growth company, indicate by check mark if the registrant has elected not to use the extended transition period for complying