If I inadvertently included an income source twice in a prior year (2015), what is the best way to recover the overpayment?

[WillK · Accepted solution]

The best way would be to amend the return to show the IRS that you double counted income. Amended returns do not “catch up” to your original return and replace them; they are processed as two separate returns.  

Amended returns have to be printed and filed by mail.  It can take the IRS up to 12 weeks or longer to process them.   If you are due a larger refund than on your original return, your amended return should only show the difference and you will receive a separate check for it.  If you owe money on your amended return, it will show only the new amount owed, you will have to mail a check with the return. Click here for amending instructions: https://ttlc.intuit.com/replies/3288565