This question is raised keeping in mind the average individuals. As known, every year ITR (Income Tax Return) is to be filed before 31st of July for the completed financial year.
This financial year relates to the following assessment year. When one files its ITR early, then he is saving himself from last minute rush and hurdles. This also helps him in getting any refund speedily. If ITRs are filed after due dates, it attracts penalty as well as interest on self-assessment dues, if any, that are paid. Early filing of ITR also helps in e-Verify process that results in speedy processing.
There is a common saying, early birds are always the winners and the respected class.