UMC Announces Dividend Ex-Date

1. Date of Board, Shareholders' Meeting Resolution or Company Decision: June 23, 2026 2. Type of Ex-Rights/Ex-Dividend (please enter 'Ex-Rights', 'Ex-Dividend', or 'Ex-Rights-Ex-Dividend'): Ex-Dividend 3. Ordinary Share Dividend Type and Amount: Cash dividend of NT$32,704,164,009 for ordinary shares, with a distribution of NT$2.60808262 per share. 4. Ex-Rights (Ex-Dividend) Trading Day: July 8, 2026 5. Last Transfer Date: July 9, 2026 6. Start Date of Transfer Suspension: July 10, 2026 7. End Date of Transfer Suspension: July 14, 2026 8. Ex-Rights (Ex-Dividend) Benchmark Date: July 14, 2026 9. Final Application Date for Bond Conversion: Not applicable 10. Start Date of Bond Conversion Suspension: Not applicable 11. End Date of Bond Conversion Suspension: Not applicable 12. Ordinary Share Cash Dividend Payment Date: July 30, 2026 13. Other Matters to be Stated: None