Hello,

As your query mention the last date to submit ignou assignments is 15th december, I presume you're about to submit assignments of january session of this year which has  already been uploaded in the official website of ignou at https://webservices.ignou.ac.in/assignments/bdp_ba.htm , you need to choose the year 2019-2020(as it includes assignments of january session of 2020), and the new session 2020-2021 includes assignments of july 2020 and january 2021.

Hope this clears your doubt.