Hi Sanjay

You don't need to worry even if you are 45 years old, you can still take admission in class 12th and complete your schooling.

Now that you are working, the best option for you is to complete your class 12th from open schools like in NIOS i.e national institute of open schooling , it  is recognised and valid as that of CBSE, ICSE and other State Boards like JAC  etc

I hope that you find this helpful.

Thankyou