Small Business Tax Deadline Calendar
Four dates everybody already knows, the three safe harbours that decide what each one costs, and the April balance the cheapest one leaves behind.
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Deadline Calendar
[Company] — tax year [YYYY]
One row per filing occurrence, not one per tax type, so a quarterly return appears four times with four dates. Every row carries the reason it applies to this entity, and every row that carries a payment carries an amount.
| Due date | Tax type | Form | Applies because | Amount | Source | Status |
|---|---|---|---|---|---|---|
| — | Federal estimated income tax | Period (a) | No withholding on business income | — | Estimated Payment Calculation | — |
| — | Federal annual return | Personal or entity | Entity type | — | Safe Harbour Comparison | — |
| — | Payroll quarterly | Quarterly | Employer of record | — | Payroll register | — |
| — | Payroll deposits | Schedule change | Lookback total against the threshold | n/a | Obligation Summary | — |
| — | Federal unemployment | Annual | Accumulated liability over $500 | — | Payroll register | — |
| — | State estimated income tax | State voucher | Resident state has an income tax | fill in | State return | fill in |
| — | Sales and use tax | State return | What you sell is taxable where you sell it | fill in | Sales register | fill in |
| — | Entity return, partnership or S corp | Not applicable | Would apply on an election | n/a | — | Kept on the calendar |
| Balance due at filing | — | — | Projected tax less what the floor requires | — | Safe Harbour Comparison | — |
Three columns here appear on no downloadable tax calendar. The reason column makes the row auditable and stops a generic list carrying dates this business does not owe. The amount column refuses to be blank, because a blank reads as zero. And the last row is the balance the safe harbour leaves behind, which is a knowable number from the moment the payment strategy is chosen and the one that actually decides whether April is survivable.
Every page that ranks for a small business tax deadline calendar is a table of dates, and every one of them is correct. April 15, June 15, September 15, January 15. March 16 for partnerships and S corporations. The dates are published, identical for everybody, and free, which is exactly why a calendar cannot help with the part that goes wrong. What none of them carries is an amount, because an amount needs your own return and your own books, and that is the only genuinely hard part of this.
The required estimated payment is the smaller of 90% of this year's tax or 100% of last year's, both set out in the Instructions for Form 2210. That second figure becomes 110% when last year's adjusted gross income was over $150,000. The threshold has not moved in decades and is not indexed, so a growing business crosses it once, stays across it, and is told nothing. An owner who sets the estimates at last year's tax divided by four is then short by exactly ten per cent every quarter while doing the careful thing.
The bigger number is the one the floor leaves behind. A safe harbour is a minimum below which interest starts, not a settlement, so meeting it in full and on time can still leave most of the year due in one payment in April. This pack computes all three floors, names the binding one, prices the April balance each strategy leaves, and puts it into the owner cash flow forecast as a dated outflow. Then it prices any shortfall per period, because each installment date stands alone.
What's in the pack
Deadline Calendar sheet
One row per filing occurrence rather than per tax type, so a quarterly return appears four times. Each row names the fact that put it there, which stops a generic list carrying dates this entity does not owe. Non-tax filings live in the business compliance calendar. Rows that do not apply stay, marked, with the condition that would make them apply, because a date deleted for being irrelevant is a date nobody re-adds after an election.
Estimated Payment Calculation sheet
Seventeen lines from projected profit to the required installment, starting from the monthly profit in the owner financial dashboard. Self-employment tax and income tax computed separately, then all three floors, then the balance each one leaves at filing. The intermediate lines are shown so an owner can check the one they doubt instead of trusting or rejecting a single total.
Safe Harbour Comparison sheet
Four strategies side by side with the quarterly payment, the total paid in-year, the balance due at filing, any penalty, and the cash needed between year end and the filing date. That last column is the one that changes minds, and it needs the trading result for the months before April rather than tax figures alone.
Underpayment Exposure sheet
Each period's cumulative requirement, what was paid against it, the shortfall, the days it runs, the rate segments at the published quarterly underpayment rate, and the charge. Then the same table recomputed with the next installment topped up, so the saving and the date it expires are both on the page. The annualised method sits at the foot.
Payment Log sheet
Every payment matched to a bank debit and a confirmation number, with cumulative paid against cumulative required and the position stated as level, ahead, or short. A scheduled payment that silently failed produces no notification anybody reads, and this is the sheet that catches it while it is still recent.
Payment Guidance document
The recommendation, the reasoning, and the single fact that would reverse it. On the worked example the recommendation is the floor rather than the projection, and the fact it turns on is whether the tax account has ever been raided, which is a question about the owner rather than about tax law. Which work generated the profit is the profitability by job or service question.
Obligation Summary document
What this entity owes, to whom, on what schedule, and which obligations are conditional on a threshold rather than fixed. Names each threshold, including the $50,000 payroll deposit lookback, and where the business sits against it, and separates what was checked against a source from what is the owner's recollection.
Eight prompts and one standing rule
The rule is that last year's tax is an input and never the answer. The prompts work the sequence: the obligation list, the deposit schedule from the lookback total, the projection, the three floors, the April balance, the annualised method, the per-period shortfall, and the quarterly roll forward.
Weekly deadline and payment reminder
Reads the calendar and the log, then reports anything due inside thirty days with its amount and the position in dollars. Where the position is short it gives the payment that would bring it level and the date after which that saving is gone. Restates the binding floor and the April balance every week, because both change silently.
How it works
- 1
Take the files or install the pack
Five blank sheets and five documents as CSV and Word files with no account, or install the whole thing into a River workspace where an agent fills them from your return and your books.
- 2
Send last year's return and this year's books
Two lines off the return do most of the work: total tax, and adjusted gross income. Then monthly profit through the last closed month, and the quarterly payroll returns if there is payroll.
- 3
Get the binding floor and the April balance
All three floors computed and compared, the binding one named with the reason the others lost, and the balance each strategy leaves at filing set against the trading result for the months before it.
- 4
Roll it forward every quarter
Two weeks before each installment date, reproject, recompute the floors, reconcile the log to the bank, and confirm one amount against one date. The reminder runs weekly in between.
Frequently asked questions
Is this template free?
Yes. Five sheets, five documents and eight prompts with no signup and no card, and they are the same files the agent works in. Editing with AI is the optional path, where your own return and books become the projection and the three floors get computed on them.
What format are the downloaded files?
CSV for the Deadline Calendar, the Estimated Payment Calculation, the Safe Harbour Comparison, the Payment Log and the Underpayment Exposure sheet, and Word for the five documents, zipped together. Excel, Numbers, Sheets, Word and Pages open them with nothing to install.
Why not just use a list of the tax deadlines?
Because the dates are the easy half and they are the same for everybody. The amount that goes with each date depends on which of three floors binds for you, and on the worked example the difference between two of them is $25,251.90 of in-season cash and $25,251.90 of April cash.
How can paying the safe harbour still leave a large bill?
Because a safe harbour is a minimum below which interest starts, not a settlement of the year. Kestrel's floor is $46,002 against projected tax of $79,171, so paying it in full and on time with no penalty at all still leaves $33,169 due on the filing date.
Does catching up in January fix an earlier shortfall?
No, and this is the rule most owners have backwards. The charge is figured separately for each installment date, so an April shortfall keeps running even if you overpay later and even if the return shows a refund. Acting on the next date still helps, which is why the pack gives a date.
Does it handle state and payroll deadlines too?
Payroll yes, including the deposit schedule, which the pack derives from your own four-quarter lookback total against the $50,000 threshold rather than looking it up. State rows are pre-listed and left for you to fill, because state floors are not always the federal ones. The calendar also carries the January 31 Form 1099-NEC date; which contractors actually need one is tracked in a separate pack.
Is this tax advice?
No. It is arithmetic on figures you supply, and the assumptions document says exactly what the worked example leaves out, including the qualified business income deduction and any state tax. It does not file anything, decide an election, or judge whether a penalty waiver applies.
Find out what April costs while you can still change it
Download the blank pack as Word and CSV files, or open it in River, send last year's return and this year's books, and get the binding floor, the four installment amounts and the balance due at filing.
Edit with AI