CFR 1.78(a)(6) says that, if a non-provisional application claims the benefit of a provisional application filed before March 16, 2013 and contains, or contained at any time, a claim that has an effective filing date on or after March 16, 2013, the applicant must file a statement to that effect within a certain time period. What happens if the statement is not filed within the stipulated time period?
Since the application data sheet (ADS) form PTO/AIA/14 includes a checkbox for making the statement under 37 C.F.R. 1.78, you may still be able to make the statement by filing a corrected/updated ADS. See MPEP 601.05(a) pertaining to 37 C.F.R. 1.76(b)(5) and 37 C.F.R. 1.76(c).
Also see MPEP 211.04, the second paragraph deals with delayed 35 U.S.C. 119(e) benefit claims.
If you do not provide the statement at all: your application may be examined according to pre-AIA 35 U.S.C. 102-103 when your application should be examined under AIA 35 U.S.C. 102. As a result, the examiner may not apply (valid) prior art references available under AIA 35 U.S.C. 102 but not available under pre-AIA 35 U.S.C. 102-103.