The Small Business Tax Preparation Checklist: Everything Your CPA Needs Before Filing

$8,376. That is the gap between what one Austin plumbing contractor's books said the business earned in 2025 and the number that actually landed on line 21 of the S corporation return. A small business tax preparation checklist exists to close that gap before your CPA finds it — because the CPA finding it in March costs you an extension, and the extension costs you a spring of not knowing what you owe.

What follows is one file worked end to end. The company is a composite drawn from the kind of contractor books I see every January at Turnkey CFO — the figures illustrate the mechanics rather than describing any single client. Every rule, form, deadline, and threshold cited is real and current for tax year 2025 returns filed in 2026. The math is shown so you can run the same passes on your own file.

What does a CPA actually need to file a small business tax return?

A CPA needs four things: a trial balance that ties to reconciled bank and credit card statements through December 31, the year's payroll and information-return filings (W-3, 941s, 1099-NEC copies), a fixed asset schedule with purchase invoices and in-service dates, and the owner-level items that never appear in the accounting file — loan documents, health insurance premiums, basis history, and prior-year returns. Everything else on any checklist is a subset of those four. Missing any one of them is what turns a two-week engagement into a September filing.

The starting point: what the P&L said on January 8

Cedar Ridge Mechanical LLC, taxed as an S corporation, one owner-operator, four W-2 field techs, two subcontracted crews. The owner exported a profit and loss from QuickBooks Online on January 8 and emailed it over. It said:

• Revenue: $842,000
• Cost of goods sold: $496,300
• Operating expenses: $227,300
• Net income: $118,400

Clean-looking report. It was wrong in six places, and none of the six were arithmetic errors. They were categorization decisions made in a hurry across twelve months. If your own P&L looks tidy but you have never tested it against the statements behind it, start with a plain-English walkthrough of what a P&L is actually telling you before you send anything to a preparer.

Stack one: the reconciliations your CPA opens first

Before anyone looks at a single expense category, four balances have to prove out. Pull these documents:

• Twelve months of bank statements for every business account, including the account you opened in August and forgot to connect.
• Twelve months of credit card statements, including the personal card you used for materials in February.
• December 31 loan statements for every note, equipment lease, and line of credit — the CPA needs the year-end principal balance, not the payment amount.
• Merchant processor year-end summaries and any Form 1099-K.

Cedar Ridge's deposits totaled $851,400 against $842,000 of booked revenue. The $9,400 difference was a supply-house rebate check deposited and coded to income. It belongs against material cost. Net income does not move — but gross margin does, and so does the revenue figure that has to survive comparison against processor and customer reporting. Under the One Big Beautiful Bill Act the 1099-K threshold was restored to $20,000 and 200 transactions, and the gross amount reported is still gross: it includes processor fees and refunded transactions. Booked revenue that is lower than a 1099-K is not automatically a problem, but it is always a question, and questions answered in January are free.

Second reconciliation failure: 61 transactions totaling $14,260 sitting in Ask My Accountant. Resolving them took four and a half hours of owner time in one sitting. Of that total, $11,180 was deductible and $3,080 was personal — a vet bill, two flights, a mattress.

Stack two: payroll, contractors, and the filings that are already late

By the time you are gathering documents for the return, the information-return deadlines have usually already passed. For tax year 2025, W-2s and Forms 1099-NEC were due to recipients and to the government by February 2, 2026 (January 31 fell on a Saturday). Send your CPA:

• Form W-3 and all W-2s
• All four quarterly Forms 941 plus the Form 940
• State unemployment filings — in Texas, the TWC quarterly wage reports
• Copies of every 1099-NEC issued, plus a Form W-9 for every subcontractor you paid

Cedar Ridge paid two subcontract crews $61,400 and $38,900. One had a W-9 on file. The other did not, and the owner had been paying a person, not a company, on a per-day rate with a company truck. That is a classification exposure, not a paperwork gap — the difference between a 1099 contractor and a W-2 employee is decided by control, not by what the invoice says. A missed 1099-NEC also carries per-form penalties that scale with how late it is filed. And note the aggregation rule: once you file 10 or more information returns in total across all types, they must be filed electronically. Four W-2s plus seven 1099-NECs is eleven forms and an e-file requirement.

Stack three: the fixed asset file, where the biggest number hides

This is the stack owners skip and the one that moves the return the most. Your CPA needs, for every purchase over roughly a thousand dollars: the invoice, the date placed in service, and how it was paid (cash, note, trade-in).

Cedar Ridge had coded two purchases to Repairs & Maintenance:

• A used Sprinter-class cargo van, $27,500, placed in service March 4, 2025
• A pipe threading machine, $6,900, placed in service September 22, 2025

Both had to come out of expense and onto the depreciation schedule — a $34,400 increase to book income. Then the return puts most of it back. OBBBA restored 100% bonus depreciation for qualifying property acquired after January 19, 2025 and raised the Section 179 cap to $2.5 million, so the timing of that March 4 date matters enormously. The van also clears the Section 280F passenger-auto depreciation caps: a cargo van with no seating behind the driver's row, at roughly 8,550 pounds GVWR, is not subject to the annual limits that would apply to a lighter passenger vehicle. Which method applies to your specific purchase — bonus, Section 179, or MACRS — is a conversation for your CPA, and the answer depends on your other income. Your job is to hand over the invoice with the in-service date on it.

Stack four: the owner-level documents nobody thinks to send

These live in your email, not your accounting file:

• Prior-year business and personal returns, including depreciation schedules and any carryforwards
• S corporation basis history — Form 7203 is required with the 1040 when a shareholder claims a loss, takes a distribution, or has a loan repaid
• Shareholder health insurance premiums paid by the business
• Mileage log — the 2025 business standard mileage rate is 70 cents per mile, so 14,000 documented miles is a $9,800 deduction and an undocumented estimate is worth nothing
• Home office square footage and total home square footage, if applicable
• Estimated tax payment confirmations with dates and amounts

Cedar Ridge paid $18,240 in family health premiums from the business account, coded to Insurance. For a more-than-2% S corporation shareholder, those premiums must be included in Box 1 of the shareholder's W-2 to support the self-employed health insurance deduction on the personal return. The IRS guidance on S corporation compensation and medical insurance is explicit about it. That is a December payroll entry. In January, fixing it means a corrected W-2. This is the same set of decisions covered in the owner-compensation decision tree for LLC and S-corp owners — reasonable compensation, distributions, and premiums are one connected question, not three.

The math: book income to return income

Here is the full reconciliation for Cedar Ridge, in order:

1. Book net income (as delivered): $118,400
2. Add back equipment miscoded to Repairs: +$34,400 → $152,800
3. Add back personal charges reclassed to distributions: +$3,080 → $155,880
4. Add back nondeductible entertainment: $2,180 in playoff tickets, 0% deductible → $158,060
5. Add back the 50% meals disallowance: the remaining $6,232 of business meals, half disallowed, +$3,116 → $161,176
6. Subtract first-year depreciation on the van and threader: −$34,400 → $126,776

Ordinary business income: $126,776 against a booked $118,400. The gap is $8,376, and the owner had been making estimated payments against the lower number all year. Note what the meals line did: a single expense account holding $8,412 of mixed charges produced $5,296 of add-backs that the bookkeeping never flagged, because the software has no way to know which lunch had a customer at the table. Split meals and entertainment into separate accounts on January 1 and this pass takes four minutes instead of an afternoon.

The health insurance was, at the entity level, a wash — $18,240 as wages instead of $18,240 as insurance expense. On the personal return it was the difference between a deduction and nothing.

What actually causes the extension

In my experience it is almost never complexity. It is one of five things, in roughly this order of frequency:

• Unreconciled December. The books stop in October and the last quarter shows up in March.
• A missing W-9. One subcontractor who will not return a call.
• No fixed asset invoices. The purchase is in the bank feed; the paperwork is in a truck.
• A commingled account that requires transaction-level review of 400 charges.
• Basis with no history — three prior preparers and no Form 7203 lineage.

If your books are already months behind, do not start with this checklist. Start with a run-today catch-up audit and work forward. An extension filed on Form 7004 moves the S corporation filing date to September 15, 2026 — but it does not extend the time to pay, and personal estimated payments still key off numbers you do not yet have.

The handoff file: one folder, eleven items

Name the folder 2025 Tax File and put exactly this in it:

1. Year-end P&L and balance sheet, accrual and cash basis
2. Trial balance and general ledger export
3. December bank and credit card statements for every account, plus any account opened or closed mid-year
4. Year-end statements for every loan and line of credit
5. W-3, W-2s, four 941s, 940, state wage reports
6. All 1099-NECs issued and all W-9s collected
7. Fixed asset invoices with in-service dates
8. Prior-year business and personal returns with depreciation schedules
9. Estimated tax payment log with dates and confirmation numbers
10. Mileage log and home office square footage
11. A short written list of anything unusual — an owner loan, a lawsuit settlement, a PPP-era carryover, a vehicle traded in

Item 11 is the one CPAs wish they got and rarely do. Three sentences from you about the weird thing that happened in July saves a week of back-and-forth.

None of this is tax advice, and it is not meant to replace your CPA's judgment on how any item is treated — the point of clean books is to give them something worth judging. If your monthly reporting is not already producing these numbers without a scramble, the reports you should be reading each month are the same ones that make filing season uneventful. Texas owners have one more date to hold: franchise tax reports are due May 15, and entities under the $2.47 million no-tax-due threshold still owe a Public Information Report.

Questions owners actually ask

My bookkeeper says the books are closed. Is that the same as return-ready? No. Closed means reconciled and locked. Return-ready means closed plus the four document stacks above — payroll filings, asset invoices, owner-level items, prior returns. A closed book with no fixed asset invoices still stalls a return.

Do I send the CPA my QuickBooks login or a set of reports? Send reports first — P&L, balance sheet, trial balance, general ledger — and offer accountant access if they want it. Accountant-user access is free and does not consume a billable seat. Sending the file without the four stacks just relocates the missing paperwork.

Frequently asked questions

When are 2025 small business tax returns due in 2026?

S corporation (1120-S) and partnership (1065) returns are due March 16, 2026, because March 15 falls on a Sunday. C corporation (1120) returns and sole proprietor Schedule C filers on Form 1040 are due April 15, 2026. Form 7004 extends the S corporation and partnership deadline six months to September 15, 2026, but it does not extend the time to pay.

What happens if I never collected a W-9 from a subcontractor?

Request it now in writing and keep the request. Without a W-9 you cannot issue a correct 1099-NEC, and unissued or late information returns carry per-form penalties that increase the longer they go unfiled. If the worker looks more like an employee than a contractor based on how much control you exercised, raise it with your CPA before you file — the classification question is bigger than the missing form.

Does my CPA need receipts, or just the bank statements?

Bank and card statements prove the payment; they do not prove the business purpose. Your CPA generally does not want the receipt stack, but you need to retain it. Keep receipts for meals, travel, and any asset purchase, and keep the mileage log — those are the categories examined most often, and a statement line alone will not support them.

I bought equipment in December. Can I deduct it on the 2025 return?

The controlling date is when the asset was placed in service, not when it was ordered or paid for. Equipment delivered and put to work in December is in service for 2025; equipment sitting in a crate until January is not. Send the invoice with the delivery date and let your CPA decide between bonus depreciation, Section 179, and regular MACRS based on your full picture.

My books show a different profit than my bank balance. Which one does the CPA use?

Neither, directly. The return is built from the trial balance after adjusting entries — reclassifications, depreciation, accruals, and nondeductible items. Bank balance is cash position, not income, and the two diverge for entirely normal reasons like loan principal payments, owner distributions, and unpaid vendor bills.