January
Jan 31 — Form 1099-NEC + 1099-MISC due to recipients & IRS (contractors paid $600+)
Jan 31 — Form W-2 due to employees
Jan 31 — Form 941 (Q4 payroll) due
February
Feb 28 — Paper 1099s/W-2s due to IRS/SSA (Mar 31 for e-file)
Varies — Many states' annual report filings
March
Mar 31 — E-file deadline for 1099s/W-2s
Varies — State charitable registrations & renewals
April
Apr 15 — Form 990 series due (orgs with calendar fiscal year ending Dec 31)
Apr 30 — Form 941 (Q1 payroll) due
May
May 15 — Form 990 due (calendar-year orgs that didn't file extension)
Varies — State annual reports continue rolling in
June
Jun 30 — Many fiscal years end here
Varies — State charitable solicitation renewals
July
Jul 31 — Form 941 (Q2 payroll) due
Jul 31 — Form 5500 (employee benefit plans, calendar year)
August
Aug 15 — First Form 990 extension deadline (calendar-year orgs)
Varies — Many states' annual filings
September
Sept 30 — Common fiscal year end
Varies — State charitable registration renewals
October
Oct 31 — Form 941 (Q3 payroll) due
November
Nov 15 — Form 990 due (orgs with fiscal year ending June 30)
Varies — State annual reports
December
Dec 31 — Most common fiscal year end
Year-end — Acknowledge donor contributions ≥$250 in writing
Varies — State filings