Prediction Market Year-End Close and Tax-Return Readiness

Last Updated on August 23, 2026 by Patrick Camuso, CPA

Quick answer (read this first)

A prediction-market trader or trading firm can finish the year with a reliable estimate of economic profit and still be materially unprepared to file a tax return. Platform statements, annual P&L reports, trading exports, and internal dashboards can provide important source information, but they do not necessarily establish the complete transaction population, the taxpayer that owned the activity, adjusted basis, the event through which a position ended, positions remaining open at year-end, or the tax adjustments ultimately required for filing.

For professional traders, market makers, proprietary trading firms, partnerships, and funds, a prediction market year-end close therefore involves more than determining annual trading profit. The records need to support the movement from source transactions to the accounting records and from the books to the tax return. Where a partnership is involved, the close may also need to support allocations and the information ultimately furnished to the partners.

The central question is whether the records are sufficiently complete, reconciled, and documented for the tax treatment reported on the return to be reproduced and supported. The broader federal characterization questions remain separate and are discussed in our prediction market tax guide.

Why Platform P&L May Not Be Enough for a Prediction-Market Tax Return

Prediction-market platforms are designed primarily to facilitate trading, account administration, and settlement. Their reporting systems may provide extensive information, including transaction histories, positions, settlements, fees, balances, and annual profit and loss. Those records can be highly useful without being sufficient, standing alone, to prepare a tax return.

A platform’s calculation of trading performance may reflect its own conventions for settlements, fees, incentives, corrections, open positions, or other account activity. Tax reporting may require additional determinations concerning ownership, basis, recognition, loss treatment, and the character of particular transactions.

Annual tax documents present a similar issue since a Form 1099 or year-end statement is part of the tax file and should be reconciled to the taxpayer’s records, but it does not necessarily determine the substantive federal tax treatment of the contracts reflected in those records.

For a participant with limited activity, these differences may be manageable. For a market maker or systematic trader operating across numerous markets, accounts, or venues, they can make year-end close a substantive accounting and tax project rather than a simple P&L exercise.

The Close Should Start With the Taxpayer and the Accounts

Before determining taxable income, the relevant taxpayer and account population need to be established. That inquiry can become more complicated when founders traded personally before forming an entity, several accounts are controlled by the same individuals, wallets or funding accounts are used alongside venue accounts, or business and personal activity were not segregated cleanly throughout the year.

Whether activity conducted through a partner’s personal account belongs to the partnership depends on the relevant ownership and other facts. Common control alone does not establish that the activity belongs on the partnership return. Similar questions can arise when funds move among bank accounts, exchanges, wallets, venue accounts, and related entities.

Transfers require factual review as well. Moving cash or another asset between accounts under common ownership may simply be an internal balance-sheet movement. A transaction that changes ownership, changes the property involved, or alters the rights held can present a different issue.

For partnerships, changes in ownership can also affect how taxable items are divided among the partners. Admission dates, withdrawals, transfers, vesting events, redemptions, and changes in ownership percentages may therefore need to be addressed as part of the close rather than reconstructed after the trading result has already been finalized.

A Complete Export Is Not Necessarily a Complete Transaction Record

Professional prediction-market traders often maintain large quantities of raw data. The harder question is whether those records represent the complete activity that must be accounted for.

A trading export may contain executions without containing settlements. A settlement report may cover a different period from the transaction history. Current and historical records may be maintained separately. Corrections or reversals may appear outside the original transaction population. An annual P&L report may summarize completed activity without establishing which positions remained outstanding on December 31.

For a high-volume operation, the close may therefore require a review of the relevant source records and reporting periods before those records are used for tax preparation. Missing date ranges, duplicates, unexplained discontinuities, and differences among transaction, settlement, and cash records can materially affect the resulting accounting.

Once source records have been transformed into accounting schedules, enough identifying information should also remain available to trace material amounts back to the records from which they were derived. That becomes important when a later tax question, correction, or reporting discrepancy requires the transaction history to be revisited.

The Tax File Needs to Reflect What Actually Happened to the Position

Prediction-market platforms commonly use familiar trading terminology, but familiar terminology does not always establish the transaction event that matters for federal tax purposes.

A contract can be acquired and held through resolution. An existing position may be transferred before resolution. A trader may acquire the opposite side of a market and reduce economic exposure. A platform may apply pairing, netting, correction, or cancellation mechanics. A position may remain outstanding when the tax year ends. Those events can matter differently for tax purposes and should remain distinguishable in the accounting record.

The issue is especially important for market makers and arbitrage traders because economic exposure can change rapidly without necessarily establishing that an existing contractual position was transferred. A strategy may be economically neutral while the underlying positions continue to exist until a later event.

The tax file should therefore preserve enough information to determine how the position was acquired, what cost or adjusted basis remained associated with it, and how the taxpayer’s rights ultimately changed or ended. The purpose is to preserve a reliable factual record on which the appropriate tax analysis can later be based.

Cash and Positions Should Be Reconciled Separately

A cash reconciliation addresses deposits, withdrawals, settlement receipts, fees, transfers, rebates, and other items affecting cash or collateral balances. A position reconciliation addresses the contracts acquired, quantities held, basis associated with those positions, positions that ended during the period, and positions remaining outstanding at year-end. A cash balance can reconcile while position quantities or basis remain incorrect. The opposite can also occur. Position records may appear internally consistent while unexplained transfers, withdrawals, credits, or other cash differences remain.

For that reason, reconciling the ending cash balance does not necessarily establish that the trading activity itself has been closed correctly.

The issue becomes more pronounced when a trader operates across several venues because transaction records, identifiers, settlement records, and reporting conventions can differ. Our broader prediction market accounting guide addresses the accounting framework for traders, funds, and institutional participants in greater depth.

Open Positions Need Their Own Year-End Review

Annual P&L does not necessarily tell the tax preparer what the taxpayer continued to own on December 31.

Depending on the activity and the treatment being applied, the year-end records may need to preserve the relevant account, contract or market, position held, quantity, acquisition history, unrecovered basis, and year-end status. Where positions are economically related, that relationship may also remain relevant to the tax analysis. The tax treatment of an open position depends on the applicable law, the contract, the taxpayer’s facts, and the accounting method properly in effect. The treatment should not be inferred merely from the venue on which the contract traded.

Even where an open position produces no current adjustment under the treatment being applied, its ownership and basis can carry into the following year. When the contract later settles, is transferred, or otherwise ends, the next year’s accounting may depend on the records established at the prior year-end.

Incomplete year-end position records can therefore affect more than the tax year currently being closed.

Basis, Fees, Rebates, and Other Adjustments Should Remain Traceable

Management reporting often focuses on net trading profit. Tax accounting may require the underlying components to remain available.

Depending on the activity, relevant year-end records may include acquisition cost, adjusted basis, amounts received when positions end, and material transaction costs. Rebates, liquidity incentives, refunds, credits, and similar amounts may also need to remain identifiable until their proper treatment has been determined. These amounts do not necessarily receive the same tax treatment simply because they appear in the same trading account. Their treatment can depend on their legal and economic function and on the transactions to which they relate.

Premature netting can therefore create problems. Reducing an entire trading book to one annual profit figure can remove information needed to address different categories of gains, losses, costs, or adjustments. The accounting records should preserve the underlying economic facts without embedding a tax conclusion into the source data. The tax analysis can then be applied to those facts when the return is prepared.

Losses Often Require More Work Than Gains

An economic loss does not necessarily establish a tax loss in the same amount or in the same year. Even after a tax loss has been recognized, separate rules can affect whether it is currently deductible and, for a pass-through entity, whether the owner can currently use the amount allocated to that owner.

The supporting record may therefore need to establish ownership, basis, the event fixing the loss, the relevant taxable year, and whether any recovery, refund, replacement, or similar right remains. Economically offsetting positions can create additional timing and limitation issues, as can the tax classification of the underlying contracts. Those determinations depend on the applicable law and the actual positions involved. They should not be inferred solely from a platform’s net P&L. For a partnership, another layer can arise after the entity has determined its own tax items because a partner’s ability to use an allocated loss can depend on partner-specific facts.

The practical result is that economic loss, tax loss, currently deductible entity-level loss, and currently usable owner-level loss can differ. A year-end estimate that treats those amounts as interchangeable may not accurately reflect the eventual return.

Our separate guide to prediction market loss deductions addresses the federal loss framework in greater depth.

The Books Need a Clear Bridge to the Tax Return

Once the trading records have been reconciled, the accounting result still has to be connected to the tax return.

The general ledger need not contain every individual prediction-market transaction if summary entries remain traceable to the underlying records. The detailed trading records can remain outside the general ledger while the books capture approved period-level activity, platform balances, operating expenses, payroll, owner transactions, and other summary amounts.

The year-end process then explains the material differences between the accounting result and the tax result. Depending on the taxpayer’s facts and the treatment adopted, those differences may arise from open positions, losses, transaction costs, incentives, unresolved contract categories, corrections, prior-period items, or other adjustments.

A useful book-to-tax reconciliation should allow a reviewer to begin with the entity’s books, understand the material adjustments reflected in the tax workpapers, and trace significant amounts back to the underlying records.

For a high-volume trading operation, that connection is generally more useful than forcing every transaction directly into the general ledger. Firms that need a more formal accounting process can also review our prediction market accounting services.

A Partnership Can Finish the Trading Close and Still Be Unready to File

A partnership adds another stage because closing the trading activity and completing the partnership return are not the same exercise.

The partnership first determines its taxable items and then allocates those items among its partners under the applicable rules. Changes in ownership during the year can affect that process, particularly where partners entered or exited, transferred interests, received interests for services, or experienced other changes in their economic rights. Transactions involving partners can require separate review as well. Payments, distributions, reimbursements, compensation arrangements, and other owner-related transactions can have different tax consequences depending on their terms and the surrounding facts.

Capital records present another issue. The equity balance maintained in the general ledger is not necessarily the same as the information required to determine a partner’s tax basis or the current use of allocated losses. A partnership can therefore have a fully reconciled trading ledger and still lack the ownership, allocation, capital, or partner information needed to complete its return and supporting schedules.

For professional trading firms, those matters are generally easier to address during the close than after the trading result has already been delivered to the return preparer.

Partners May Need Information Beyond the Amounts on Their K-1

The partnership determines and reports its own tax items, but some of the ultimate consequences depend on the individual partner.

Partner-level basis, loss limitations, federal taxes applicable at the owner level, prior-year attributes, and state filing obligations can require information beyond the partnership’s trading records. The partnership generally cannot resolve every owner-level issue within its trading ledger, and the owner may need supplemental information to complete the individual return correctly. A well-managed close therefore identifies significant owner-level information requirements before filing season is substantially underway.

If ownership dates, contribution records, capital information, prior suspended items, or state information remain unresolved, those gaps can delay both the partnership return and the partners’ individual filings even when the prediction-market activity itself reconciles cleanly.

Platform Tax Documents Should Be Reconciled, Not Treated as the Tax Analysis

Annual P&L reports, account statements, and Forms 1099 should be incorporated into the close and compared with the taxpayer’s accounting records. Differences may result from reporting periods, the types of payments covered, fee presentation, taxpayer identification information, corrected documents, or other reporting conventions.

More importantly, an information return does not necessarily determine the substantive federal tax character of the underlying prediction-market transaction. Prediction-market taxation can depend on the contract terms, transaction mechanics, taxpayer facts, and applicable federal tax rules. A platform’s reporting convention can be relevant evidence without resolving that analysis. Where the taxpayer’s supported return treatment differs materially from third-party reporting, the difference should be identified and addressed as part of return preparation rather than left unexplained.

For venue-specific reporting issues, see our guides to Kalshi tax reporting and Polymarket taxes.

State and Local Tax Issues Should Be Identified During the Close

Professional trading firms can have state and local filing obligations even when trading itself occurs electronically. Relevant facts can include where the business operates, where its owners reside, where personnel perform services, whether the business maintains offices in additional jurisdictions, and whether ownership changed during the year.

The Tax Position Still Needs a Final Review

A reconciled accounting result does not complete the tax analysis where the return depends on a material legal interpretation.

Prediction-market taxation continues to involve areas in which published federal guidance does not provide one answer for every contract or taxpayer. Before a material treatment is carried onto the return, the preparer should confirm that the position remains supportable under current authority and that the relevant factual assumptions are supported by the accounting record.

Prior-year reporting also deserves attention. If the current analysis differs from the treatment used on an earlier return, the difference should be identified and the appropriate procedural consequences considered rather than allowing the old treatment to continue automatically or changing the approach without adequate review.

The same applies to disclosure. Whether disclosure is appropriate depends on the actual return position, the applicable professional and statutory standards, the supporting authority, and the relevant facts. Disclosure does not substitute for adequate factual support or a defensible tax position.

The year-end accounting process should provide the factual record necessary for that final professional review without attempting to predetermine every return-level judgment.

When Is a Prediction-Market File Ready for Tax Preparation?

A prediction-market file is approaching return readiness when the material tax amounts can be derived from sufficiently complete records without relying on unsupported assumptions or unexplained reconciliation differences.

The relevant taxpayer and accounts should be established. The source-data population should cover the period being reported. Cash and positions should reconcile to the extent required by the activity. Material positions should have support for quantity, acquisition cost or adjusted basis, and the event through which the position changed or ended. Positions remaining open at year-end should be documented, and material transfers, corrections, rebates, incentives, and other adjustments should be understood.

Material losses should have been reviewed for recognition, timing, and current deductibility. The accounting result should reconcile through the tax workpapers to the amounts expected to appear on the return.

For partnerships, the ownership and allocation records should also be sufficiently complete to prepare the entity return and provide the partners with the information needed for their filings. Platform statements and information returns should reconcile to the taxpayer’s records where relevant, and material state and local filing obligations should have been identified.

If those matters remain materially incomplete, the remaining work may involve reconstruction, accounting remediation, tax analysis, or return-position implementation before ordinary return preparation can proceed.

What This Means in Practice

For a professional prediction-market trader or trading firm, year-end close is generally more manageable when the underlying records have been maintained throughout the year rather than assembled for the first time during filing season.

Material filing problems can arise when substantial historical activity must be reconstructed after the fact, ownership records were not maintained as the business changed, year-end positions were not preserved, cash and positions were never independently reconciled, or a material tax treatment was assumed before the underlying transaction mechanics were established.

A properly designed close maintains a clear connection among source records, detailed trading accounting, the general ledger, and the tax workpapers without requiring the accounting process to resolve every substantive tax issue in advance. At higher levels of trading volume and organizational complexity, tax preparation can become the final stage of a broader accounting, reconciliation, and tax-analysis process.

How Camuso CPA Helps

Camuso CPA advises professional prediction-market traders, market makers, proprietary trading firms, partnerships, and other institutional participants on prediction-market tax and accounting matters. Our work can include tax analysis, transaction accounting, historical reconstruction, book-to-tax reconciliation, partnership tax matters, and year-end return readiness, depending on the engagement scope and the taxpayer’s facts.

Trading firms with broader operational needs can learn more about our CPA services for trading firms and our dedicated prediction market CPA practice.

Request a Prediction Market Tax & Accounting Assessment

Frequently Asked Questions

What should a prediction market year-end close include?

A prediction market year-end close should establish the relevant taxpayer and accounts, reconcile the transaction and cash records, identify positions remaining open at year-end, support basis and material adjustments, address material loss and partnership issues, and connect the accounting records to the amounts expected to be reported on the tax return. The appropriate scope depends on the activity and the applicable law and facts.

Is a Kalshi or Polymarket P&L enough to prepare a tax return?

Not necessarily. Platform P&L can be an important source record, but the tax file may also require support for ownership, basis, settlements, positions remaining open at year-end, transfers, losses, and other adjustments. The scope depends on the taxpayer’s activity and the records available.

When should a professional prediction-market trader begin the year-end close?

For high-volume traders and trading firms, material accounts, positions, cash balances, and unresolved differences are generally easier to address throughout the year. Waiting until filing season can turn a year-end close into a historical reconstruction project.

Why are open positions important at year-end?

Open positions establish what the taxpayer continues to hold when the year ends and preserve information that may be needed when those contracts later settle, are transferred, or otherwise end. Their tax treatment depends on the applicable law and facts.

Is every losing prediction-market position currently deductible?

No. The existence, timing, character, deductibility, and ultimate use of a tax loss can involve separate questions. The result depends on the applicable tax framework, the transaction facts, and, for pass-through entities, potentially owner-level limitations.

Does a Form 1099 determine how prediction-market activity must be taxed?

Not necessarily. A Form 1099 should be reconciled with the taxpayer’s records, but information reporting and substantive federal tax characterization are separate questions. The tax treatment depends on the applicable law and facts.

Why can a prediction-market partnership require more year-end work than an individual trader?

A partnership has to address the trading activity as well as ownership changes, allocations, partner transactions, capital information, owner reporting needs, and potentially state filing requirements. A completed trading P&L therefore does not necessarily mean the partnership return is ready.

Does a prediction-market market maker need a different year-end close?

Market-maker status does not by itself determine the tax treatment. However, high transaction volume, two-sided activity, fees or incentives, economically related positions, multiple accounts, and partnership structures can increase the amount of reconciliation and tax-accounting work required before filing.

What happens if prediction-market records are incomplete at year-end?

The required work depends on the nature of the gap. Some taxpayers may need a limited reconciliation, while others may require historical reconstruction, accounting remediation, or separate tax analysis before return preparation can be completed responsibly.