# Tax Deadlines for Bookkeepers: A Year Calendar

- Author: AutoBankConvert (https://www.autobankconvert.com)
- Published: 2026-08-14
- Updated: 2026-08-14
- Category: Tax season
- Canonical: https://www.autobankconvert.com/blog/tax-deadlines-for-bookkeepers

> Tax deadlines for bookkeepers across the year: 1099s, payroll forms, estimates and returns, and when each client's books must be closed to meet them.
The tax deadlines for bookkeepers that shape the year are January information returns, March returns for partnerships and S corporations, April returns for individuals and C corporations, quarterly estimates and payroll returns, and the October extension date. Each one sets an earlier date when the client's books must already be closed and handed over.

## Which tax deadlines for bookkeepers fall in January?

January is the most crowded month for a bookkeeper, because several filings depend on totals for the year that just ended. Contractor payment forms, payroll year-end forms and the last estimated payment for the prior year all land in a few weeks. The December statements have to be in and reconciled before any of them can be right.

### Contractor forms

The [IRS instructions for Forms 1099-MISC and 1099-NEC](https://www.irs.gov/instructions/i1099mec) set January 31 as the date to file Form 1099-NEC with the IRS and to give recipients their copies, moving to the next business day when January 31 falls on a weekend or holiday. Whoever files the forms needs a list of payees and totals before then, built from the year's payment lines.

### Payroll year-end forms

Payroll forms follow their own dates. [IRS Publication 509, the tax calendar](https://www.irs.gov/publications/p509), lists the annual federal unemployment return, Form 940, as due on the last day of the first month after the calendar year ends. For 2025 wage statements, the 2026 edition gives February 2, 2026 as the date to give employees their Forms W-2, because January 31 fell on a Saturday. Most small clients use a payroll provider that files these, but the bookkeeper still has to make sure the books agree with the provider's totals.

### The last estimate for the prior year

Publication 509 places individual estimated payments in the 4th, 6th and 9th months of the tax year, with the final one in January after the year ends. That January payment is easy to miss in the books, because it pays last year's tax from this year's bank account. Code it so the preparer can find it.

## Return due dates by entity and the bookkeeping deadline behind each

Business and individual returns have fixed due dates set by the IRS, and each one implies a date when the books must be closed. Publication 509 puts partnership and S corporation returns on the 15th day of the 3rd month after the tax year ends, and individual and C corporation returns on the 15th day of the 4th month.

For a calendar-year client, that means March 15 for partnerships and S corporations and April 15 for sole proprietors, who report on the individual return, and for C corporations. The bookkeeping deadline sits weeks earlier, because the preparer needs time to work.

| Client type (calendar year) | Return due | Books handed over by (example) |
| --- | --- | --- |
| Partnership | March 15 | February 10 |
| S corporation | March 15 | February 10 |
| Sole proprietor or single-member LLC | April 15 | March 1 |
| C corporation | April 15 | March 1 |

The handover dates are examples. Agree the real ones with each preparer. Partnership and S corporation books come first because the owners' own returns depend on the figures those entity returns pass through to them.

Sole proprietor books feed a different form on the owner's return. The guide to [Schedule C bookkeeping](/blog/schedule-c-bookkeeping) explains how a sole proprietor's accounts map onto it, which is useful when deciding what the preparer needs from you.

## Quarterly tax deadlines for estimates and payroll returns

Two kinds of deadline repeat every quarter: estimated tax payments for owners and some entities, and the employer's quarterly payroll return. Both depend on current books. An estimate is only as good as the profit figure behind it, and a payroll return has to agree with the wages and taxes recorded for the quarter.

### Estimated payments

Owners usually make estimated payments themselves, often from the business account. The bookkeeper's job is to post each payment correctly, usually to an owner or tax account rather than an operating expense, and to have a current profit and loss ready if the client or preparer wants to revisit the amount before the next due date.

### Quarterly payroll returns

Publication 509 lists Form 941, the employer's quarterly federal tax return, as due on the last day of the first month after each calendar quarter ends. For a calendar year that gives the end of April, July, October and January. Payroll providers usually file it. Reconcile the payroll bank account and the payroll liability accounts for the quarter before that date, so a mismatch is found while it is still cheap to fix.

## A twelve-month tax deadline calendar for a bookkeeping practice

A practice calendar puts every external deadline next to the internal task that must finish first. The external dates come from the IRS; the internal ones are yours. Seeing both in one table stops January from consuming February's work and shows the quiet months when catch-up and cleanup fit.

The calendar below assumes calendar-year clients and federal dates only. State dates vary and should be added for each state you work in. Internal tasks are examples.

| Month | External deadline | Bookkeeping task that must finish first |
| --- | --- | --- |
| January | 1099-NEC (Jan 31), Form 940, Q4 Form 941, final prior-year estimate | December statements in and reconciled; contractor totals sent |
| February | Form W-2 copies when Jan 31 moves to the next business day | Partnership and S corp books closed and handed over |
| March | Partnership and S corp returns (Mar 15) | Sole proprietor and C corp books closed |
| April | Individual and C corp returns (Apr 15), Q1 estimate, Q1 Form 941 (Apr 30) | March close; Q1 payroll accounts reconciled |
| May | None federal for most clients | Catch-up work for late clients |
| June | Q2 estimate (Jun 15) | May close; mid-year profit and loss for estimate review |
| July | Q2 Form 941 (Jul 31) | June close; Q2 payroll reconciled |
| August | None federal for most clients | Clean-up of uncategorized lines |
| September | Q3 estimate (Sep 15); extended partnership and S corp returns | Answer preparer questions on extended entity returns |
| October | Extended individual returns (Oct 15), Q3 Form 941 (Oct 31) | Finish open items on extended individual clients |
| November | None federal for most clients | Ask clients about new accounts and big purchases |
| December | None federal for most clients | Collect W-9s for new payees; plan January |

### Reading the calendar

The busiest stretch runs from January to mid-April. The quieter months, May, August and November, are where the practice can work on clients who fell behind. A client who has not filed for several years is a different project; the guide to [bookkeeping for clients with unfiled tax returns](/blog/unfiled-tax-returns-bookkeeping) covers how to rebuild those years in order.

## How should a bookkeeper set internal close dates before tax deadlines?

Set each client's internal close date by working backward from the return due date: subtract the time the preparer asks for, then subtract the time your own close takes for that client, then add a buffer for late statements. Write the result in the engagement letter or the client's calendar invite so it is agreed, not assumed.

### A worked example for three clients

These clients are fictional. The day counts are examples of the reasoning.

| Client | Return due | Preparer needs | Your close takes | Buffer | Internal close date |
| --- | --- | --- | --- | --- | --- |
| Pine Street Partners (partnership) | Mar 15 | 4 weeks | 1 week | 1 week | Feb 1 |
| Ortega Plumbing Inc. (S corp) | Mar 15 | 3 weeks | 2 weeks | 1 week | Feb 1 |
| Mara Chen, consultant (sole prop) | Apr 15 | 3 weeks | 1 week | 1 week | Mar 11 |

The buffer covers the client who sends December's card statement two weeks late. If statements reliably arrive late for a client, increase the buffer for that client rather than hoping.

### Telling clients what the date means

Clients often hear "your return is due in April" and assume their bookkeeping can wait until then. Explain that the books must close well before the return, and say what the closed books will show them. The post on [explaining financial statements to clients](/blog/how-to-explain-financial-statements-to-clients) has wording that helps when you send the year-end reports with that date.

Getting a full year of statements processed quickly is what makes early close dates realistic. [AutoBankConvert](/get-started) is built for that month-end pile: it converts a batch of statements per client, checks each against its printed balances and exports files for QuickBooks or Xero.

## Tax deadline traps: weekends, fiscal years and extensions

The usual dates shift in three common cases: when a deadline lands on a weekend or holiday, when a client uses a fiscal year instead of the calendar year, and when a return is extended. Each one changes the bookkeeping date too, so the practice calendar should be built from each client's facts rather than copied year to year.

### Weekends and holidays

When a due date falls on a Saturday, Sunday or legal holiday, it generally moves to the next business day, as both the 1099 instructions and Publication 509 show. Treat the moved date as a gift to the preparer, not to yourself. Keep your internal date where it was.

### Fiscal-year clients

A client whose tax year ends on June 30 has return dates counted from that month, not from December. The 15th day of the 3rd or 4th month falls in September or October. Mark fiscal-year clients clearly in your calendar, because their year-end work collides with nothing else and is easy to forget.

### Extensions

An extension moves the filing date, not always the payment date. The [IRS page on getting an extension](https://www.irs.gov/filing/get-an-extension-to-file-your-tax-return) tells individuals that an extension gives them until October 15 to file and that tax owed should still be paid by the April date. For the bookkeeper, an extended client still needs closed books early enough for the preparer to estimate that payment.

### Deadlines that are not the bookkeeper's to track

Some dates belong to the preparer or the payroll provider: state franchise taxes, local business taxes and sales tax returns in many practices. Decide in writing who tracks each one. A deadline that everyone assumes someone else is watching is the one that gets missed.