Executive answer
Thin capitalization and transfer pricing answer different questions. The first applies a domestic interest limitation associated with excess debt under Section XXVII of Article 28 of the Mexican Income Tax Law, subject to its calculation, options and exclusions. The second asks whether an independent enterprise would borrow that amount and at which rate and conditions.
Passing the statutory relationship does not prove an independent lender would provide principal or that rate, term, currency and security are market terms. Exceeding the limit does not by itself characterize every debt as equity for all purposes; it produces consequences under the specific provision and requires correct calculation.
The practical order is: inventory debt; delineate loans; determine arm’s-length principal and price; calculate interest; apply thin capitalization; apply other limitations and requirements; reconcile deduction and returns. Do not mix conclusions in one opaque worksheet.
Two-test matrix
| Element | Arm’s length | Thin capitalization |
|---|---|---|
| Question | What would an independent party agree? | Which interest is limited by law? |
| Unit | loan/transaction | taxpayer/year |
| Principal | capacity and delineation | statutory average balances |
| Equity | structure and alternatives | accounting equity or option |
| Rate | benchmark and terms | interest subject to factor |
| Counterparty | related under transaction | foreign related party in rule |
| Time | agreement/modification date | average and fiscal year |
| Outcome | amount/rate/conditions | nondeductible interest |
| Evidence | contract, rating, comparables | ledger, equity, months, calculation |
They connect through data, not conclusion.
Current statutory basis
Section XXVII of Article 28 addresses interest derived from debt exceeding three times accounting equity where the debt is contracted with foreign related parties under Article 179. The statutory calculation uses the annual average balance of interest-bearing debt and the relevant equity measure under the text.
The section includes rules for excess, proportional interest, average balance, an equity option and continuity, exclusions and specific provisions. Read it in full. A simplified calculator may omit a critical condition.
This article is not advice. Check later amendments, regulations and facts before year-end.
Debt inventory
Include bank and intercompany loans, bonds, interest-bearing accounts, cash pool, leases or instruments according to applicable classification. Identify lender, residence, relationship, currency, monthly balance, rate, interest and purpose.
Reconcile month-end balances to ledger and subledgers. The average is not year-end. Investigate capitalized principal, embedded interest, payments and FX. Bridge currency to pesos.
Flag foreign related-party debt but do not remove other debt from the general population without reviewing the formula. Support legal exclusions.
Accounting equity
Obtain opening and closing statements and policies. Identify contributions, reductions, dividends, losses, valuation effects and mergers. Reconcile equity used.
The section provides an option based on specified tax accounts and losses under conditions and a minimum continuity period. Do not choose each year by outcome. Document election, difference, business reason and support, especially where the text demands evidence.
Negative or volatile equity needs early analysis. A late contribution may affect calculation but needs corporate substance and documentation.
Excess calculation
Prepare a transparent schedule showing month-end interest-bearing debt, annual average, applicable average equity, triple, excess and average foreign related-party debt. Then apply the section’s rules for full or proportional nondeductible interest.
Do not mix non-interest principal without reading the text. Do not use daily averages where monthly is specified without explanation. Control partial months and mergers. Trace every number to an account.
Run pre-year-end sensitivity for projected debt, equity, dividends, FX and losses. Planning should not manufacture circular movements.
Arm’s-length principal
Before the limit, determine whether an independent lender would provide the amount. Model debt capacity, cash flow, coverage, assets, rating, term and covenants. If only part is economically plausible debt, delineation may require further analysis.
The three-times limit is not authorization to borrow exactly that amount. A no-cash-flow company may not obtain 3:1; a stable asset-rich company might obtain more externally, while domestic limitation can still affect related foreign debt.
Document purpose and alternatives. Do not confuse accounting debt-equity with arm’s-length characterization.
Arm’s-length rate
Benchmark currency, term, rating, seniority, security, date and fees. An off-market rate may be adjusted even below the limit. An arm’s-length rate can still create limited interest.
Reconcile contractual reference, day count and payment. Interest entering the thin-cap schedule should start from correct records. A calculation error is not cured by the tax factor.
Review guarantees and implicit support. They affect pricing but do not automatically change the statutory formula.
If a schedule says “deductible” because debt/equity is below three, principal, rate and terms still require arm’s-length proof.
Exclusions and scope
The current text excludes certain debts under conditions, including specified financial-system and infrastructure or electricity cases, and contains a rule for certain unregulated multiple-purpose financial companies. Do not generalize by industry.
Obtain authorization, purpose and use documents. A project label is insufficient. Read transition and regulations. Where debt funds mixed activities, test tracing.
Document legal conclusion by exclusion. Do not copy prior-year schedule after facts change.
Interaction with net interest
The separate net-interest limitation in Article 28 is another test. Determine current sequence and rules. Do not apply percentages simultaneously without controlling base and carryforwards.
Bridge accounting interest; arm’s-length adjustments; specific nondeductible amounts; thin capitalization; net-interest limitation; other items; final tax interest. Identify temporary and permanent differences.
Interest not limited by one rule is not automatically deductible. Review general requirements, withholding, treaty and documentation.
Withholding and treaties
Thin-cap calculation does not replace withholding on foreign payment. Determine source, rate, treaty, residence, recipient and timing. Reconcile accrued and paid interest.
A nondeductible portion may still have other consequences. Coordinate returns and evidence. Do not automatically net fees or FX.
Retain certificates and renewals. Show the actual counterparty.
Current accounts and cash pool
Recurring intercompany balances may bear interest or need formalization. Identify structural positions. Month-end is especially relevant for averages.
In cash pools, separate debt and deposits, leader and bank. Do not offset without legal right. Positions can change and affect calculation.
Monitor before closing. A cosmetic month-end sweep without economic change creates substance risk.
Capital planning
Forecast monthly debt, equity and interest. Evaluate real needs, contributions, dividends, refinancing and third parties. Avoid circular or temporary contributions without reason.
The committee should see debt capacity, thin-cap limit and net-interest limit separately. One action may improve one while harming liquidity or governance.
Record business decision. Tax policy follows financing rather than replacing it.
Recommended file
- Debt inventory.
- Relationship and residence.
- Monthly balances.
- Interest by agreement.
- Opening/closing equity.
- Option and continuity.
- Exclusions.
- Excess calculation.
- Factor and limited interest.
- Arm’s-length capacity.
- Rate benchmark.
- Other limitations.
- Withholding and returns.
Illustration
An entity has MXN 900 million average total debt and MXN 250 million average accounting equity. The preliminary three-times threshold is MXN 750 million; excess is MXN 150 million. Average foreign related-party debt must then be compared under the section to determine full or proportional effect.
The example cannot conclude without composition, exclusions, equity option and interest. In parallel, capacity may support only MXN 600 million; that is an arm’s-length issue not solved by threshold.
If rate is also off-market, address the base before applying limitations according to the analysis. The bridge prevents confusion.
Risk signals
- December balance instead of monthly average.
- All debt confused with foreign related debt.
- Equity unreconciled.
- Option changed annually.
- Exclusion without support.
- Arm’s length concluded from under 3:1.
- Rate without benchmark.
- Cash pool ignored.
- Double limitation without bridge.
- Withholding detached from accounting.
Review control
Recalculate months, averages and factor. Compare total interest with ledger. Check sign, currency and entities. An independent reviewer traces a sample.
Reconcile schedule to annual return, deferred tax and notes. Explain book-tax differences and control final version.
Update forecasts quarterly and monthly near year-end. Assign debt, equity and rate owners.
Monthly data bridge
Build a table by account and month: opening balance, movements, FX, capitalization, payment and closing balance. Identify whether it bears interest and the counterparty. Month-end amounts feed the statutory annual average; a separate column feeds average foreign related-party debt.
For equity, bridge opening to closing through contributions, profit/loss, dividends, reserves, valuation and restructuring. Reconcile approved statements. If the tax-account option is used, show opening/closing accounts, losses and the five-year continuity requirement under current text.
Every manual change needs a ticket, evidence and reviewer. Protect formulas. Keep pre-close and final versions to explain movements.
Deduction sequence
Document the legal sequence applied. Start from accounting and accrued interest; adjust transactions not meeting arm’s length; identify items failing specific requirements; calculate thin capitalization; then apply other limitations under current law. This article does not prescribe a universal order: confirm it technically.
The bridge should prevent limiting the same interest twice. Identify carryforwards where applicable and permanent differences. Reconcile current and deferred tax.
Pre-close scenarios
Forecast remaining monthly balances, not only year-end. Simulate external refinancing, actual repayment, capitalization, contribution and dividends. Compare tax with liquidity, covenants, FX and governance.
An equity contribution may improve the ratio but requires funds and purpose. Repaying debt with another related-party loan may not reduce total debt. Movements should have economic effect.
Group review
The Mexican entity calculates under its own position. Still map lenders and chains. A foreign entity may borrow from another affiliate and on-lend to Mexico; for pricing follow function and funding, while thin capitalization applies Mexican text to Mexico’s debt.
Coordinate Master File and policies. If global documentation calls financing strategic capital while the local agreement calls it short-term, resolve the contradiction.
Equity option controls
The alternative equity measure is not simply a more favorable number. Confirm eligibility, compute each component from tax records, test the percentage difference condition and support any business reason required by the text. Record the election year and lock the continuity calendar.
Reconcile CUCA, CUFIN, reinvested CUFIN where relevant under the statutory wording, and pending tax losses. Do not infer balances from financial statements. Obtain tax ledgers and prior returns. Corporate actions can change these accounts differently from accounting equity.
Exclusion control
Create one memorandum per asserted exclusion. Quote the current paragraph, state entity, debt, project, authorization and use of proceeds, and link evidence. Quantify the balance and interest excluded. A general industry description is insufficient.
Review mixed-use debt. If funds are fungible, define tracing method and limitations. An exception for part of activity should not automatically cover all financing. Revalidate annually.
Relationship with debt characterization
Thin capitalization assumes identified debt for its calculation; transfer pricing may question whether an independent party would lend all principal. Address the characterization analysis before using the statutory threshold as comfort.
If an instrument contains profit participation, convertibility, subordination or no maturity, analyze legal and economic classification. Article 28 may have other provisions relevant to the payment. Do not force every instrument into a conventional loan template.
Audit-ready package
Provide a summary showing rule, population, option, exclusions, excess, factor and interest effect. Attach debt and equity bridges, contracts, ratings, benchmark, withholding and return reconciliation. A reviewer should reproduce from source ledgers.
Prepare explanations for capital movements, month-end spikes and differences between related-party disclosures and the schedule. Interview treasury and accounting before submission. Record who approved final tax position and unresolved legal judgments.
Questions for management
- Is each borrowing economically debt?
- Does principal fit independent capacity?
- Is rate arm’s length?
- Are monthly balances complete?
- Does equity reconcile?
- Is the option consistent over time?
- Are exclusions documented?
- Are other interest limits bridged?
- Are withholding and returns aligned?
- Which action is business-driven before year-end?
Answers should distinguish completed evidence from planned remediation.
Sources and cutoff
This article was verified as of August 2, 2026. The primary source is current Mexican Income Tax Law, Article 28, Section XXVII. For the separate arm’s-length test consult the OECD Guidelines 2022, Chapter X and the OECD Mexico profile. Check later amendments.
Zugzwang’s Interest Deductibility Review integrates inventory, equity, averages, limit, capacity, rate and other restrictions into a defensible tax reconciliation.