Can I perform Panchami Shradh if I don’t know which tithi my ancestor died on?

Yes. If you are uncertain about your ancestor’s death tithi, you have two options: perform Shradh on Sarva Pitru Amavasya (October 10, 2026), which is specifically designed for all ancestors including those whose tithis are unknown; or if you believe your ancestor died unmarried, include them specifically in the Panchami Shradh ritual on September 30, 2026.