If your turnover is under ₹2 crore, filing GSTR-9 is optional and you will not be penalized for not filing. However, if you choose to file voluntarily, ensure the data is correct. If you identify any short-paid taxes during this process, you must pay them via DRC-03 along with the applicable interest (18% for delayed tax, or 24% for incorrect ITC claims) to avoid future notices or scrutiny from the GST department.