Executive answer
A defense file demonstrates how a related-party transaction occurred, why it created benefit or value, how price was determined and how it was booked and reported. It does not replace the transfer pricing report, Local File or legal obligations. It connects them with contemporaneous evidence so conclusions can be reproduced before review.
Organize the file by transaction and risk rather than as an indiscriminate repository. Every assertion—who decided, what was delivered, which property was used, why a margin is reasonable—links to a source. Identify contradictions and address future gaps without changing historical documents.
Research and verification cutoff: August 2, 2026. Confirm obligations and treatment for the specific year and transaction.
Difference from the annual report
The report describes the transaction, FAR, method, comparables and conclusion. The defense file adds agreements, decisions, deliverables, systems, invoices, accounting, payments and reconciliations proving those facts. Repeating report pages does not create evidence.
Its purpose is to anticipate cross-checks. If the report says the parent controls inventory, show approvals and reports. If a service benefited Mexico, show request, activity and outcome.
Index by transaction
Separate goods, services, royalties, intangibles, loans, guarantees, adjustments and extraordinary dealings. Create a profile with parties, period, amount, agreement, policy, method, accounts, filings and custodians.
A master index links common documents without duplication. Stable identifiers make the file independent from preparer memory.
Assertion-evidence matrix
Extract material assertions from reports and agreements: function, property, risk, price, benefit, right and decision. Assign primary and secondary evidence, owner and quality. Flag contradiction or absence.
The matrix prevents collecting files that do not answer the question and shows where one item supports several claims.
Inventory and reconciliation
Rebuild transactions from ledger, CFDI invoices, payments, agreements and counterparties. Compare with the report and filings. Explain base, period, currency, VAT, adjustment and reclassification differences.
Every amount has a route from transaction to report. Preserve queries, filters and control totals. Manual tables without lineage are weak.
Agreements
Include effective versions, schedules, signatures and dates. Summarize rights, obligations, price, adjustment, termination, ownership and risk, then compare conduct.
Identify later agreements as later. They do not rewrite the past. Where an agreement is missing, document facts and plan prospective remediation.
Proven functional analysis
For each function identify person, role, entity, decision, system and evidence. Assets include use and control; risks include capability, information and consequences.
Interviews rely on examples. Compare charts and job descriptions with access rights, minutes and email. FAR should update by year.
Goods and supply chain
Connect order, invoice, shipping, receipt, inventory, sale and payment. Include Incoterms, origin, quality, warranties and adjustments. Identify sourcing, volume and pricing decisions.
Where customs applies, reconcile declared value and price changes. Do not execute a tax adjustment without reviewing customs impact.
Services
Build a file by category: need, request, provider, people, activity, deliverable, recipient, benefit, duplication, base, key, markup, invoice and payment. One generic presentation does not prove a year.
Use samples with documented population and criterion. Tickets, calendars, reports, files, results and confirmations may help, subject to data protection.
Intangibles and royalties
Define rights, territory, base, rate, DEMPE, protection and exploitation. Connect agreement, registrations, sales, calculation, invoice, withholding and payment. Separate bundled services.
Valuation retains assumptions, date and sources. The file shows decision makers and development funding.
Financing
Include purpose, approval, agreement, disbursement, use, capacity, rate, security, interest and payment. Reconcile balances and currency. A benchmark does not prove debt.
For cash pooling or guarantees, document benefit, functions, implicit support and remuneration. Conduct should follow terms.
Adjustments
Retain monitoring, calculation, real or virtual classification, approval, invoice, journal, payment, filing and indirect effects. Explain range point and period.
A true-up should not first appear when the report finishes. Monthly evidence shows an operating policy.
Request a TP Defense File Sprint to connect report conclusions with evidence, amounts and conduct before review.
Extraordinary transactions
Restructurings, share or asset sales and indemnities require purpose, chronology, rights, options, valuation, approvals and execution. Separate initial consideration from future remuneration.
Retain contemporaneous information and scenarios. Later outcomes should not replace date-specific knowledge.
Filings and compliance
Include an obligation map and acknowledgements. Reconcile the report with DIM, Local File, Master File, CbCR, ISSIF, SIPRED or applicable reporting. Identify owners and dates.
Do not assume every obligation applies. Document why it does or does not.
Accounting and CFDI
Link accounts, journals, invoices, notes, payments and agreements. Review description, currency, period, VAT and party. Descriptions should match the transaction.
Explain differences through bridges. Do not alter historical journals outside applicable procedures.
Contemporaneous evidence
Classify evidence created during operation, close and later. Date does not automatically invalidate but affects strength. Preserve originals and metadata.
Do not fabricate retrospective minutes. A later memorandum can organize facts if it identifies sources and limitations.
Evidence quality
Rate relevance, authenticity, completeness, date, coverage and reproducibility. An authentic invoice may poorly prove benefit; a relevant report may cover one month.
Ratings guide sampling and action. There is no perfect document, but there can be a coherent set supporting specific claims.
Version control
Separate originals, workpapers, final and delivered versions. Use permissions, names and logs. Retain formulas and datasets. Links should work outside the preparer’s device.
Annual updates create versions and bridges; never overwrite earlier-year evidence.
Data room
Organize by transaction and risk with index, owner and retention. Sensitive information has restricted access. External providers follow protocol.
Test recovery and opening. An inaccessible file during audit fails its purpose.
Independent review
A reviewer traces sampled assertions to evidence, recalculates amounts, compares agreements and tests populations. Findings have severity and owner.
The review seeks contradictions, not missing files alone. Close every finding with evidence or retain it as an accepted risk.
Readiness traffic light
Green means assertion and reconciled evidence; amber means limitation with a plan; red means material contradiction or absence. Report by transaction rather than averaging.
The CFO sees exposure, decision and date. Color does not replace technical analysis.
Annual calendar
At opening update agreements and owners; monthly retain evidence and monitor; at close reconcile; afterward integrate report and filings; before archiving review.
Material events trigger off-cycle updates: new transactions, restructurings, losses, adjustments or personnel changes.
Remediation
Correct processes, systems, agreements or responsibilities prospectively. Preserve prior-period facts and assess options with advice. Never manufacture evidence.
Every action has cause, owner, date and proof. Remediation is tested, not announced.
Delivery readiness
The internal defense file may contain analysis not requested. For an official request, select according to the act and strategy with legal review. Do not deliver the entire repository automatically.
The submitted package retains index, version and acknowledgement. The internal record identifies what left.
Assertion testing workshops
Run a workshop for each high-risk transaction with tax, legal, finance and operations. Present the assertion without its supporting document and ask the operational owner to explain the process; then compare the answer with evidence. This reveals where polished drafting has outrun actual conduct.
Record disagreements, missing custodians and data needed. The workshop is not designed to coach a single story. It is a controlled challenge that distinguishes terminology differences from real contradictions and assigns a remediation path.
Coverage and sampling dashboard
For recurring transactions, show the population, value covered by direct evidence, value covered by sampling and exceptions. Segment by month, provider, service, product or agreement as relevant. A high document count can still represent low monetary or temporal coverage.
Set thresholds before selecting samples and include adverse items. Explain why results can or cannot be generalized. Where evidence quality varies, increase coverage or isolate the weak subset rather than assigning one rating to the year.
Financial-statement consistency
Cross-check provisions, impairments, contingencies, tax, related parties and subsequent events against the file. A restructuring described as minor may be material in board minutes or notes; a guarantee may appear as a contingency while absent from the transfer pricing report.
Finance explains differences in perimeter and date. This does not turn the defense file into a financial audit; it prevents approved corporate information from contradicting the tax position.
Counterparty coordination
Compare agreement, amount, description, date and characterization in both entities. Currency or local rules may explain differences, but a bridge is needed. Confirm provider and recipient for services, balance and interest for loans, and base and withholding for royalties.
Do not impose one global narrative where local facts differ. Maintain a jurisdiction-position register and escalate conflicts before filings.
Retention and continuity
Define retention by category under law and policy and plan for personnel or provider changes. Export information from systems scheduled for replacement and preserve dictionaries.
Test restoration annually. A successor should understand the index, controls and decisions. A file known only to its author deteriorates even when documents remain.
Escalation criteria
Escalate material contradiction, missing evidence for a significant deduction, omitted transactions, irreproducible methods, inconsistent agreements or cross-border exposure. The escalation states facts, amount, options and date rather than only a red status.
The committee decides whether to supplement, correct, reserve or pursue another path. Keep its decision separate from technical workpapers and link it to follow-up.
Root-cause remediation
Classify weaknesses as people, process, data, system, agreement or policy. A missing invoice calls for a different fix from absent benefit evidence or risk-control contradiction. Assign one accountable owner and define what evidence proves closure.
After remediation, select a fresh transaction and retest. Updating a template does not prove that teams changed conduct. Record residual risk and the next review date so the defense file becomes a control loop rather than an annual document exercise.
Example
A company pays management fees, a royalty and a loan. Its defense file separates transactions, reconciles amounts, reconstructs sampled services, maps DEMPE, proves use of funds and connects adjustments. Review finds an outdated agreement and weak key; prior risk is documented and future conduct corrected.
Warning signs
Warnings include unindexed folders, the report as sole proof, agreements without conduct, services supported only by invoices, unreconciled data, models without formulas, later files without dates, inconsistent filings and retrospective remediation. Keeping everything without linking it to assertions is another.
These signs show that document volume does not equal defense.
Conclusion
A defense file turns a technical conclusion into a reproducible record of facts, amounts and decisions. Its value lies in anticipating cross-checks and contradictions before review.
Annual readiness reduces reconstruction, improves controls and supports coherent, selected evidence in a response.
Request a TP Defense File Sprint to assess gaps and build the file by transaction and risk.
Verified official sources
- Mexican Chamber of Deputies, current Income Tax Law, Articles 76, 76-A, 179 and 180 as relevant.
- Mexican Chamber of Deputies, current Federal Tax Code, applicable recordkeeping, accounting and verification powers.
- OECD, Transfer Pricing Guidelines 2022.
Verification closed on August 2, 2026. A defense file does not replace legal requirements or a response specific to an official act.