These dates are also found on the PDC's Calendar of Events.  (Printer-friendly version)

Within 2 weeks of becoming a candidate Register the campaign (File a C-1)
January 10 File a C-3 for each deposit made in the previous month and a C-4 report that covers the period through Dec 31
February 10 File a C-3 for each deposit made in the previous month and a C-4 report that covers the period through Jan 31
March 10 File a C-3 for each deposit made in the previous month and a C-4 report that covers the period through Feb 29
April 10 File a C-3 for each deposit made in the previous month and a C-4 report that covers the period through Mar 31
May 11 File a C-3 for each deposit made in the previous month and a C-4 report that covers the period through Apr 30
May 11-15 Declaration of candidacy filing week
June 1 Begin filing C-3 reports weekly, each Monday, for deposits made during previous 7 days (Monday through Sunday)
June 10 File month C-4, if necessary, that covers the period through May 31
June 22 Last day before primary election to change from mini to full reporting without special circumstances
July 14

Candidates appearing on the primary election ballot file a C-4 that covers the period June 1 through July 13.

Candidates not on the primary election ballot file monthly reports in June, July, August, and September.
July 25 - Aug 3 Campaign books open for public inspection
July 28 Candidates appearing on the primary election ballot file a C-4 that covers the period July 14 through July 27
July 28 - Aug 3 Special reports due if candidate receives contributions of $1,000 or more from a single source
AUGUST 4 PRIMARY ELECTION DAY
August 31 Last day before general election to change from mini to full reporting without special circumstances
September 10

Post-primary C-4 due that covers the period July 28 through August 31

Candidates not on the primary election ballot file a report for the month of August
October 13 21-day pre-general C-4 report due - report for the period Sept 1 through Oct 12
October 13 - November 2
  1. Special reports due if candidate receives contributions of $1,000 or more from a single source
  2. Unless the contribution is from the state committee of a bona fide political party, a candidate may not receive contributions from a single source exceeding $5,000 in the aggregate.  
October 24 - November 2 Campaign books open for public inspection
October 27 7-day pre-general C-4 report due - report for the period Oct 13 through Oct 26
November 2 Last Monday that weekly C-3 reports must be filed
NOVEMBER 3 GENERAL ELECTION DAY
December 10 Post-general C-4 due that covers Oct. 27 through Nov 30.  File C-3s that have not been filed for any deposits made in November.
January 11, 2021 End of election cycle C-4 due that covers Dec. 1 through Dec. 31.  File C-3s for any deposits made in December.