The Starting Point: A Tax Return Is Built from Books, Not Raw Documents

Before a business tax return can be prepared, there has to be a complete, reconciled set of books for the tax year. That means a profit and loss statement, a balance sheet, and a trial balance that tie together and reflect every transaction in the period. The other records described in this article support those statements. They do not replace them.

This distinction matters because a common assumption is that handing a preparer a folder of bank statements, receipts, and invoices is roughly equivalent to handing over organized books. It is not. Bank statements and credit card statements show cash movement. They do not categorize transactions, separate capital expenditures from operating expenses, distinguish owner draws from payroll, account for accruals, track inventory, or capitalize fixed assets. A business tax return cannot be reliably prepared from bank statements alone.

The same is true of working backward from prior-year figures. Estimating expense categories or revenue based on percentages from a prior return is not an acceptable preparation methodology. Every line on a business return reflects actual transactions in the actual year. The books are where those transactions live.

Under IRC §6001 and Treas. Reg. §1.6001-1, the obligation to maintain records adequate to determine the correct tax liability belongs to the taxpayer. The accounting method used to produce those records is governed by IRC §446. What the CPA produces from your records is the return and the workpapers that support it. That division of labor is what makes the finished return accurate and defensible when it needs to be.

Core Records Every Business Should Expect to Provide

The list below covers what every business should have ready before tax preparation begins, regardless of entity type or industry. These are the inputs the preparer works from. The return and its supporting workpapers are what the CPA produces from them.

Each item below serves a specific function on the return. Providing all of them at the start of an engagement is what keeps the process moving and the result defensible.

  • Year-end financial statements - a profit and loss statement, balance sheet, and trial balance exported from your bookkeeping software or prepared by your accountant, covering the full tax year. These are the foundation. Every other document on this list either supports or verifies what is in these statements.
  • Bank and credit card statements for the full tax year - all accounts, all months, no gaps. These are used to verify that the books reconcile to actual cash activity. They are not a substitute for books; they confirm the books are correct.
  • Prior year federal and state tax returns - needed for depreciation continuity, carryforward items such as net operating losses or passive activity losses, and basis and capital account tracking for S corporation shareholders and partners. A return prepared without the prior year return is working without context.
  • Forms 1099 received - 1099-NEC, 1099-MISC, 1099-K, and any other information returns reporting income paid to your business. These are cross-referenced against reported revenue.
  • Forms 1099 issued - copies of any 1099-NEC or 1099-MISC forms your business issued to vendors or contractors during the year, along with the associated 1096 transmittal. These support deductions for payments made and confirm filing compliance.
  • Loan documents - for any business debt, the documents showing interest paid during the year, the outstanding principal balance, and the amortization schedule if applicable. Interest deductibility depends on proper characterization of the underlying debt.
  • IRS and state tax correspondence - any notices, letters, or responses received during the tax year. These may affect the return directly, or may need to be disclosed or addressed before filing.

One point worth stating plainly: categories on a business return reflect actual transactions that occurred during the actual year. Revenue and expense figures are drawn from the books, not estimated from prior-year percentages or ratios. If the books do not support a number, the number does not go on the return.

Records You Only Need If Your Business Has These Features

The records in the previous section apply to every business return. The records below apply only when your business has specific characteristics. If none of these situations apply to you, this section does not affect your engagement.

Records you only need if your business has these features
  • Inventory records
    If your business buys or manufactures goods for sale, the return requires a beginning inventory balance, an ending inventory balance, and the cost of goods sold figure that connects them. That means purchase records, receiving records, and a physical or perpetual count at year end. For businesses that meet the thresholds under IRC §263A, additional records are required to allocate indirect costs to inventory under the Uniform Capitalization rules. If your bookkeeping software tracks inventory, the relevant reports should come out of that system. If inventory has been tracked manually or inconsistently, that gap needs to be resolved before preparation begins.
  • Vehicle and mileage logs
    If the business deducted vehicle expenses or you used a personally owned vehicle for business purposes, a contemporaneous mileage log is required under IRC §274(d). That log must record the date of each trip, the destination, the business purpose, and the mileage. The same substantiation standard applies to business travel, meals, and any other listed property. A log reconstructed from memory at tax time does not satisfy the contemporaneous requirement. If the underlying records do not exist, the deduction is disallowed regardless of how legitimate the underlying expense was.
  • Payroll reports and W-2 / W-3 filings
    If you have employees, the return will need your quarterly payroll tax returns (Forms 941 or 944), your annual unemployment filings (Form 940), and copies of the W-2s and W-3 issued for the year. These are used to verify wages deducted on the return, confirm payroll tax deposits, and reconcile officer compensation for S corporations. If a third-party payroll processor handles these filings, the relevant reports should be available through that service.
  • Home office substantiation records
    If you are claiming a home office deduction, you need documentation supporting the square footage of the dedicated space and the total square footage of the home, along with the actual expenses allocable to the home: mortgage interest or rent, utilities, insurance, and repairs. The space must be used regularly and exclusively for business. If you are using the simplified method, the square footage figure is still required.
  • Significant fixed asset acquisitions
    If the business purchased equipment, vehicles, machinery, furniture, or other depreciable property during the year, the return needs the purchase date, the cost, and documentation of the business use percentage. These items feed the depreciation schedule and determine eligibility for Section 179 expensing and bonus depreciation. Invoices and settlement statements are the source documents. Assets that were traded in, disposed of, or sold during the year also need to be identified, because the prior depreciation history affects the gain or loss calculation.

S Corporations and Partnerships: Basis and Capital Account Records

S corporations and partnerships carry a layer of recordkeeping that other business structures do not: each owner's basis and capital account must be tracked separately, updated each year, and carried forward continuously. These figures are not produced by the tax return. They are inputs to it, and they have to exist before preparation begins.

For S corporation shareholders, stock basis and debt basis determine whether a loss can be deducted in the current year, whether a distribution is taxable, and how gain or loss is calculated on a future sale of shares. The accumulated adjustments account (AAA) runs parallel to basis tracking at the entity level and affects how distributions are characterized. None of these figures can be reliably reconstructed after the fact if the records were not maintained year over year.

For partnerships, each partner's outside basis and the capital account schedule on Schedule K-1 serve similar functions. The capital account roll-forward connects directly to the prior year return, which is one reason the prior year return appears in the core document list for every business. For partnerships reporting capital accounts on a tax basis under current Schedule K-1 requirements, the continuity of that schedule matters: a gap or an inconsistency in a prior year creates work that has to be resolved before the current year can close correctly.

What you should expect to provide for an S corporation or partnership return:

  • Shareholder or partner basis schedules maintained through the prior year, or the most recent return that reflects those figures
  • A record of any loans from shareholders to the S corporation, including original amounts, repayments, and current balances, since debt basis is tracked separately from stock basis and affects loss deductibility under IRC §1366(d)
  • Capital contribution and distribution records for the current year, by owner
  • The prior year Schedule K-1 for each owner, which the preparer uses to verify opening balances

If basis schedules were not maintained in prior years, that gap has to be addressed before the current year return can be completed accurately. Reconstructing basis from historical returns and transaction records is possible in many cases, but it is a separate task with its own time requirement. The earlier that situation is identified, the more options exist for resolving it before the filing deadline.

When Books Are Not Ready: What Happens Before Tax Prep Can Start

Tax preparation and bookkeeping are two separate services. They happen in sequence, not simultaneously. If the books for the tax year are not complete and reconciled when an engagement begins, the work required to get them there is its own engagement, and it has to finish before return preparation can start.

This is not a procedural preference. A tax return reports the results of actual transactions in the actual year. Those transactions have to be categorized, reconciled, and reflected in a set of financial statements before there is anything to prepare a return from. Estimating expense categories or revenue figures based on percentages from a prior year is not an acceptable methodology. Categories on a business return reflect what actually happened, not back-calculated ratios.

When a client comes in with incomplete or unreconciled books, the path forward looks like this:

  1. The bookkeeping work is scoped and priced as a separate engagement before any tax work begins.
  2. That work is completed, either by the firm or by a third-party bookkeeper, depending on the situation.
  3. Once a complete, reconciled set of books exists, tax preparation begins.

The additional fees for catch-up bookkeeping are discussed with the client before any work starts. For more on how incomplete records affect the overall scope and cost of an engagement, see What Does NEPA CPA Charge for Tax Preparation?

The practical consequence worth understanding: if you hand a preparer a folder of bank statements and receipts and ask them to file your return, one of two things happens. Either the return gets built on incomplete or unverified information, which creates accuracy and audit risk, or the bookkeeping work gets done first, which takes time and costs money. There is no shortcut around the underlying requirement that books exist before a return can be prepared from them.

Who Is Responsible for the Records, and for the Return

Under IRC §6001 and Treas. Reg. §1.6001-1, the obligation to maintain adequate records belongs to the taxpayer. That obligation exists independently of whether you have a CPA, and it does not transfer to the preparer when you hand over your documents. The records support the facts reported on the return. The taxpayer signs the return and attests to those facts.

The CPA's role is to take a complete, accurate set of books and records and produce a return that correctly reflects the tax consequences of what those records show. That is a meaningful responsibility, but it is a different one. A preparer cannot create accurate facts from incomplete inputs, and signing a return does not make the underlying records more complete than they were.

For a fuller treatment of how preparer responsibility and taxpayer responsibility interact, including what penalties apply to each party and under what circumstances, see the related article Who Is Actually Responsible for What's on Your Tax Return?