Expediency in filing a 1040x, amended return.

[taxclueless]

I realized this morning that I made a mistake on my return. I filed it just 10 days ago. Does it help to file the amended return, 1040x, as fast as possible? I messed up the cost basis of one of my stock sales so I owe about another $150. I understand that if you get a refund that you have to wait until the refund is received before filing the 1040x. Does it matter if I owe? The IRS has already cashed the first payment check.

I've never filed a 1040x before. Will I have a bullseye on my forehead for an audit? I'm on pins and needles about it.