Get your taxes done using TurboTax

You can even have a penalty when getting a refund for not paying in evenly during the year.  Did you have a penalty on your 1040 line 38?   It is just an estimate so it is possible for the IRS to recalculate it and send you a refund or a bill for more. 

 

Understanding your CP30

https://www.irs.gov/individuals/understanding-your-cp30-notice