It's been more than 21 days since my return was accepted. When will it get approved? Does this mean I am getting audited?

[surgam]

I don't have any refund owed, but I paid the tax owed at the time of filing. 

[xmasbaby0]

There will not be an "approval" that you can track if you owed tax due and paid it.  Your own bank/credit card records are your proof that you paid your tax owed.  You are done, unless someday the IRS sends you a letter that says you made a mistake on your tax return.