Can a daughter perform Pitrupaksha rituals if there is no son?

Yes. While the tradition designates the eldest son as the primary Karta, the Dharma Shastras also permit daughters, daughters-in-law, nephews, or any close male or female relative to perform the rituals when no son is available. What matters most to the scriptures is the sincerity of intention and the proper Sankalpa — not the gender of the performer. Our pandits guide families through this regularly.