In a notice issued to BSP chief Mayawati, the Commission asked the BSP to respond by March 15.
The poll panel referred to a petition filed in the Allahabad High Court which had alleged the party had deposited large sums of money in its bank account within a short period of time on different occasions after demonetisation on November 8 last.
"You are requested to send your comments on the issue raised in the petition along with your version regarding the contributions received in cash by your party and the deposits made in the party's accounts," the notice issued by Election Expenditure unit of the Commission.
The Enforcement Directorate had on December 26 detected cash deposits totalling over Rs 104 crore in an account belonging to the BSP in a branch of United Bank of India here.
Officials said the Enforcement Directorate, as part of its routine survey and enquiry operations to check suspicious and huge cash deposits in banks, had visited the Karol Bagh branch of the UBI and found huge deposits made in these two accounts post-demonetisation.
The sleuths found that while Rs 102 crore was deposited in Rs 1,000 notes, the rest Rs 3 crore was deposited in the old Rs 500 notes.