Investopedia explains SEC Form NT 10-Q
The form 10-Q is required to be filed within 45 days following the end of each of a company's first three fiscal quarters. If the 10-Q cannot be filed in a timely manner, the company must file a Form 10-QT with the commission. A very common reason for an NT 10-Q is a merger or acquisition, which prevents results from being incorporated in time for the filing. The SEC provides for "unreasonable effort and expense", with explanation, as part of the application for relief.