Put every tax deadline on the calendar

Why this matters

Tax deadlines don't move because you were busy, and the penalties for missing them are automatic. The failure mode is rarely ignorance — it's each side assuming the other was tracking the date. A shared calendar with lead-time reminders turns deadlines from ambushes into routine.

What "done" looks like

• Every filing and payment date for your entity type on one shared calendar
• Each date has an owner: who prepares, who approves, who files or pays
• Reminders set 2–4 weeks ahead, not day-of

How to do it

1. List your dates with your accountant — entity type decides them. Calendar-year partnerships and S corps file by March 15; C corps and individuals by April 15.
2. Add quarterly estimated payments: April 15, June 15, September 15, and January 15.
3. Add payroll and information returns: W-2s and 1099-NEC forms to recipients by January 31, plus your payroll deposit schedule.
4. Add state dates — income, franchise, and sales tax calendars are separate and vary by state.
5. Assign owners and lead times: documents to accountant by X, draft back by Y, filed by Z.
6. Check weekend shifts each January — dates roll to the next business day (in 2026, March 15 fell on a Sunday, shifting to March 16).

Common mistakes

• Tracking only April 15 and getting ambushed by the March 15 passthrough deadline
• Confusing an extension to file with an extension to pay — payment is still due on the original date
• Setting reminders on the due date, when there's no time left to gather anything

Real-world examples

• IRS Publication 509 publishes the official tax calendars each year — the source your shared calendar should reconcile to.
• The estimated-tax schedule is uneven: the second payment lands June 15, two months after the first — a trap for founders budgeting "every three months."

From a founder's point of view

The calendar is a contract about attention. Once every date has an owner and a lead time, the reminder fires, the routine runs, and April becomes just another month.

Rule of thumb

Every date on one shared calendar, each with an owner and a 2–4 week head start. If a deadline can still surprise either of you, this isn't done.