Company: SNY
Filing Date: 2025-10-29
Form Type: 424B5
Source: 0001193125-25-255563
Chunk: 62

Company: Sanofi
Filing Date: 2025-10-29
Form: 424B5
Chunk 62
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 114—Foreign Bank and Financial Accounts Report as a result of holding notes. The
application of these reporting requirements is not entirely clear. You are thus encouraged to consult your U.S. tax advisor with respect to these and any other reporting requirement that may apply to your acquisition of notes.

Information Reporting and Backup Withholding

Information returns must be filed with the IRS in connection with payments of interest on the notes made to certain United States persons. If
you are a United States person, you generally will not be subject to U.S. backup withholding tax on such payments if you provide your U.S. taxpayer identification number and certify that you are not subject to backup withholding in the manner
required. You may also be subject to information reporting and backup withholding tax requirements with respect to the proceeds from a sale of the notes.

If you are not a United States person, you may have to comply with certification procedures to establish that you are not a United States
person in order to avoid information reporting and backup withholding tax.

THE FOREGOING DISCUSSION DOES NOT DISCUSS ALL ASPECTS OF U.S. FEDERAL INCOME TAXATION THAT MAY BE RELEVANT TO A PARTICULAR U.S. HOLDER IN LIGHT OF ITS INDIVIDUAL INVESTMENT CIRCUMSTANCES OR TO CERTAIN TYPES OF U.S. HOLDERS SUBJECT TO SPECIAL TREATMENT UNDER THE U.S. FEDERAL INCOME TAX LAWS, NOR DOES SUCH DISCUSSION ADDRESS ANY ASPECTS OF STATE, LOCAL, OR NON-U.S.TAX LAWS OR OF ANY U.S. FEDERAL TAX LAWS OTHER THAN THE INCOME TAX LAWS. ACCORDINGLY, PROSPECTIVE PURCHASERS ARE URGED TO CONSULT THEIR OWN TAX ADVISORS AS TO THE

PARTICULAR TAX CONSEQUENCES TO THEM OF THE ACQUISITION, OWNERSHIP AND DISPOSITION OF NOTES, INCLUDING THE APPLICATION OF FEDERAL, STATE, LOCAL, NON-U.S.AND OTHER TAX LAWS AND POSSIBLE FUTURE CHANGES IN SUCH TAX LAWS.

S-42

UNDERWRITING Subject to the terms and conditions stated in the underwriting agreement dated the date of this prospectus supplement (the “Underwriting Agreement”), each underwriter named below has severally agreed to purchase, and we have agreed to sell to that underwriter, the respective principal amount of the notes set forth opposite the underwriter’s name:

| Underwriters                    |     | Aggregate      
 principal      
 amount of