On which lunar day is Lakshmi Puja celebrated during Diwali?

Lakshmi Puja during Diwali is celebrated on Amavasya, the new-moon day.

In most of India and Nepal, this is the third day of the five-day Diwali or Tihar observance. Amavasya is the darkest lunar night, so rows of oil lamps, candles, and electric lights symbolically bring brightness to the darkness. Lakshmi, the goddess associated with wealth and prosperity, is worshipped along with Ganesha in many households.

Tradition says Lakshmi visits homes that are clean, illuminated, and welcoming. Families therefore clean and decorate their houses, draw rangoli at entrances, light diyas, and offer sweets, fruits, and other ritual items. The puja is generally performed in the evening, when the new-moon night begins.

A common mix-up comes from regional calendars and regional forms of Lakshmi worship. In Assam, Odisha, and Bengal, Kojagori Lakshmi Puja is held on Ashvin Purnima, the full moon, rather than Diwali Amavasya. The question refers to the principal Diwali Lakshmi Puja observed across most of India.