If you are still waiting for a Schedule K-1 (for Form 1065 partnership . . . or any kind of K-1 for that matter), then it is usually preferable to request an extension and file just a single (original) tax return, rather than filing an original tax return just to meet the April deadline, with the certain knowledge that you would later have to amend it.
Also, if you are absolutely positive that you are due an income tax refund, on both a federal level and a state level (if applicable), then it is true that you don't need to specifically request an extension of time to file from the IRS. In other words, there is no penalty for filing your tax return "late" as long as you are due a refund.
That said, if there is any doubt at all as to a refund vs. a liability, then there is no harm in requesting an automatic 6-month extension, as doing so is free to you. Therefore, this is something that you may wish to consider as an option. Here is a link to some more details on this process:
https://turbotax.intuit.com/tax-tools/tax-tips/Tax-Extensions/How-Do-I-Get-an-Extension-on-Taxes-/IN...
Thank you for asking this question.
