Once the fundraise has a close date you'll receive a 5-day notice. In addition, you will see a 7-day countdown on the fundraise page. You have up until the fundraise closes to cancel.

Once the minimum funding target is met, some companies do a "rolling close", where investments that have successfully applied are executed and funds transferred, but the campaign is still open to receive new investments. 

You'll still receive a five-day notice when any close is about to happen.