Should OTM option be squared off on expiry?

@nithin sir,
If i have sold option and on expiry its OTM, should I square it of or should I let it expire at 3:30 pm?
what will happen If i do not square it(OTM option) of myself and let it expire? is there any penalty or taxes?

You can let it expire if it is OTM, will expire worthless and no transactions or taxes