I was audited last year and the audit is still ongoing. Should I file my 2018 taxes now or file and extension until the 2017 audit is completed?

If you think the audit results will impact something on the 2018 return, I would file an extension making sure I pay in enough taxes by April 15th however.

If I know the issue being looked at, does not impact the 2018, then I would timely file the 2018 return.