How can I enter a 1099B short sale transaction that has sold Box 1c 8/20/18 before acquired date 1/22/19. TT will not allow. Cost Basis not reported to IRS

Change the Date Acquired on your 1099-B to the Correct Date.

Click this link for more info on Changing Date Acquired on 1099-B. 

In order to close a short you must go to the market and acquire some securities.

Date Acquired is the date you closed the short sale.

Date Disposed is settlement date after Date Acquired. Options settle in one business day. Stocks in two.

So, your gain/loss is always Short Term, no matter how long you were short.

If your broker is reporting your transaction incorrectly, you should change the dates.

Then get another broker.

That would show sale in 2018 . I have since read TT only concerned with dates is to determine short term or long term gain. So change and enter buy (or exercise date ) 2019) . Still investigating. 

Maybe my answer above was not clear.

The correct acquired date is 1/22/2019.

The correct date disposed is 1/23/2019 or 1/24/2019, depending as noted above.

Which  brokerage?