K1 hasn't arrived yet. Should I file for an extension or just amend my tax return when I receive my K1 in September?

[hbl3973]

By all means, file for an extension.  The important thing is to pay by April 18th.  For this you will need to (over?)estimate the K1 income numbers in order to know how much to send the IRS with your extension form.  And don't forget your state income tax return(s) if any.