Executive answer
Under the 2026 Miscellaneous Tax Resolution, Form 83/ISR is the prior notice for transfer pricing adjustments under the first paragraph of Rule 3.9.1.4; Form 84/ISR is the prior notice under the second paragraph. The first relates to voluntary or compensating adjustments made after the Rule 3.9.1.3 deadlines. The second relates to domestic corresponding adjustments arising from a counterparty’s tax correction.
Both are prior notices, not automatic authorizations. Filing does not prove method, amount, deduction, counterparty treatment or documentation. The taxpayer should satisfy Rule 3.9.1.3 and other provisions, prepare filings and retain evidence.
Numbers changed from earlier years. Use the current Annex 2 and form for the fiscal year and filing date. Do not copy guidance using historical codes.
Core distinction
| Element | 83/ISR | 84/ISR |
|---|---|---|
| Rule | 3.9.1.4, first paragraph | 3.9.1.4, second paragraph |
| Case | Voluntary/compensating after deadline | Domestic corresponding after counterparty primary |
| Source | Taxpayer decision | Related-party tax correction |
| Counterparty | Domestic or foreign depending on dealing | Mexican related party |
| Key evidence | Method, adjustment, requirements and lateness | Primary correction, symmetry and requirements |
| Timing | Before using the prescribed route | Before the corresponding deduction |
Confirm the current text; the table does not replace the form.
Decision tree
- Does the adjustment increase a deduction or require Rule 3.9.1.3?
- Is it made after ordinary deadlines?
- Is it the taxpayer’s voluntary or compensating adjustment?
- Is there a primary adjustment to a Mexican counterparty?
- Is the counterparty’s tax correction documented?
- Does the requested effect match year and amount?
- Are documentation, invoice, accounting and withholding requirements met?
- Will returns reflect the adjustment?
- Is the notice filed before taking the deduction/route?
- Are the form and platform current?
If questions two and three are yes, assess 83/ISR. If four and five are yes, assess 84/ISR. Other facts may require another route.
Timeline
| Date | Event | Evidence |
|---|---|---|
| Original dealing | Income/deduction | Agreement, invoice, entry |
| Closing | Result and range | Report and reconciliation |
| Ordinary deadline | Rule 3.9.1.3 | Calendar and receipt |
| Later discovery | Cause and amount | Memorandum |
| Primary correction, if any | Counterparty act/correction | Return and support |
| Decision | 83 or 84 | Approved matrix |
| Prior notice | Filing | Receipt and attachments |
| Amended returns | Reflection | Workpapers and receipts |
| Execution | Document/accounting | Invoice, entry, memorandum account |
| File closure | Review | Index and approval |
Adapt the sequence to the form, while preserving the “prior” character.
If the adjustment was found after the deadline or follows a correction to a Mexican related party, pause the deduction until the form and file are validated.
Form 83/ISR
This case starts with a voluntary or compensating adjustment after prescribed deadlines. The rule permits consideration in the original year under conditions and a prior notice. It does not permit shifting the item to a convenient year.
Document late discovery, dealing, related party, method, range, amount, direction and classification. Explain deduction requirements, returns and counterparty treatment.
Use the form published in current Annex 2. At filing, verify channel, recipient, subject, description, format and attachment instructions.
Form 84/ISR
This notice relates to a domestic corresponding adjustment following a primary adjustment to the counterparty. A tax correction and correspondence should exist. A private agreement to move profit is insufficient.
Integrate evidence of the primary adjustment, corrected return, year, dealing, amount and treatment. Show that the corresponding effect does not exceed or recharacterize the primary without basis.
Coordinate both taxpayers. Amounts and signs should align. The notice does not remove audit authority.
Common file
- Taxpayer and representative identification.
- Entity and counterparty.
- Relationship and dealing.
- Fiscal year and dates.
- Agreement and original documents.
- FAR, method, comparables and range.
- Adjustment calculation.
- Real/virtual and variant.
- Invoice/document or memorandum accounts.
- Original and amended returns.
- Withholding and other taxes.
- Counterparty evidence.
- Draft notice and attachments.
- Approval and filing receipt.
The current form may request more; this list organizes but does not replace it.
Rule 3.9.1.3 requirements
Deductibility is conditioned on requirements including returns, documentation, invoices where accounting effects exist, memorandum accounts for tax-only effects, counterparty proof and withholding under the current text.
The notice does not cure a missing requirement. Build a requirement-evidence-owner matrix. If service or arm’s length conditions cannot be proven, the form does not transform the expense.
Confirm that the adjustment is reflected in the year in which the underlying income or deduction arose under the applicable rule.
Invoicing and accounting
For real adjustments, the tax document should correlate with original documents and contain required descriptions. Validate the current rule, Federal Tax Code Articles 29 and 29-A, and foreign-document requirements.
For virtual adjustments, the Resolution contemplates memorandum accounts and book-tax reconciliation among requirements. Do not issue a fictitious invoice.
PT-028 develops execution. Attach the bridge to the notice file.
Counterparty
For 83/ISR, prove related-party treatment where required. For 84/ISR, the counterparty’s correction is the source. Obtain appropriate return, workpaper, receipt and confirmation while respecting confidentiality.
Reconcile currency, amount, year and dealing. Explain any small difference. Do not net separate transactions.
For foreign corresponding adjustments, analyze the relevant rule, treaty and MAP; 84/ISR is the domestic corresponding form.
Preparing the submission
Open the current form on the preparation date. Verify electronic signature, Tax Mailbox or other channel, attachment size and format, form name, addressee and text.
Use an index and readable files. Sign where required. Retain integrity and timestamp evidence. Do not depend on one screenshot.
If the platform fails, record attempts and use applicable official channels; do not assume an extension.
After filing
Retain the receipt and exact submitted file. Record reference and owner. File returns and execute according to the conclusion; the notice does not replace later actions.
Respond to requests with version control. Do not send revised calculations without explaining changes. The authority may audit the information.
Reconcile final results with annual return, ISSIF, SIPRED, Annex 9 and Local File where applicable.
83/ISR case
After the deadline, Mexico discovers an undercharged service and seeks an increased deduction in the original year. It first validates materiality, method and adjustment; classifies; prepares a document or memorandum account; reviews withholding and returns; then files the prior 83 notice.
If the service did not exist or lacks support, the notice does not solve it. If the amount belongs to another year, correct the analysis first.
The timeline explains lateness and preventive measures.
84/ISR case
The authority adjusts income of one Mexican company. Its Mexican related counterparty seeks a corresponding deduction. It assembles the act or correction, returns, same dealing and amount; validates rules; and files 84 first.
If only a private agreement exists without tax correction, the case is not presumed. Explain sign differences caused by tax or currency.
Both parties retain coordinated files.
Common errors
- Interchanging 83 and 84.
- Using a prior-year code.
- Filing after deduction without testing “prior.”
- Believing the notice authorizes the treatment.
- Omitting Rule 3.9.1.3 requirements.
- Failing to prove the primary in an 84 case.
- Failing to explain lateness for 83.
- Sending unreadable attachments.
- Misaligning returns.
- Losing the submitted version.
Quality control
The Adjustment Notice Review delivers the tree, timeline, form, checklist, file, draft, returns and follow-up. Legal and tax review the rule; accounting and counterparty confirm amounts.
An independent reviewer confirms that the facts match the paragraph, the notice is prior, attachments are complete and data reproduce.
Submission control matrix
| Control | 83/ISR | 84/ISR |
|---|---|---|
| Paragraph matched | First | Second |
| Trigger evidence | Late voluntary/compensating adjustment | Counterparty primary correction |
| Prior timing confirmed | Date and sequence | Date and sequence |
| Rule 3.9.1.3 file | Complete | Complete |
| Counterparty proof | As applicable | Mandatory to the case |
| Returns mapped | Original/amended | Both taxpayers |
| Receipt preserved | Folio and timestamp | Folio and timestamp |
Complete the table with links, not checkmarks alone. A reviewer should open every supporting item from the matrix.
Change control after submission
If the amount, year, document or counterparty evidence changes after filing, compare the submitted file with the new fact. Determine whether a clarification, new filing or return change is required; do not silently replace the internal folder.
Maintain a change log showing author, date, reason, old amount, new amount and legal conclusion. Preserve the original package and receipt. Communications with the authority should reference the same folio.
At closing, issue a final reconciliation from notice to deduction and every return. This proves that the route notified is the route actually implemented.
Related topics
- PT-026 through PT-029: decision, classification, execution and taxes.
- PT-085: APA.
- PT-088: corresponding adjustment and double taxation.
Notice preparation timeline
Start with the adjustment date and nature, fiscal year, parties, amount and applicable rule. Determine the relevant form, authorized filer, deadline, channel, documents and signature. Use the current Exhibit 2 version and retain the source; an old internal guide should not control the procedure.
Build the package with the calculation, study, economic explanation, agreement, accounting evidence, returns and foreign-adjustment support where relevant. Before submission, a reviewer compares names, tax IDs, periods, currencies, amounts and attachments. Test portal access and file capacity early.
Archive the screen, submission, receipt and every request. A notice does not by itself cure a transaction or prove deductibility, so preserve the separate technical file. If rejected, or if the portal differs from the form, log the date, message and escalation. This timeline protects the deadline and retains the full decision history.
Sources and verification date
Assign a backup with access to the file and authorized signature. Test the process before the deadline and define escalation for portal failure. The calendar includes time to correct rejected files; filing on the final day turns a technical incident into avoidable tax risk. Retain support contacts and evidence of every attempt.
- 2026 Miscellaneous Tax Resolution, Rules 3.9.1.1 through 3.9.1.4, subject to amendments.
- Annex 2 to the 2026 Resolution, Forms 83/ISR and 84/ISR.
- SAT adjustment notice portal.
- Mexican Federal Tax Code, Articles 28, 29, 29-A, 32 and 34-A.
Sources checked on August 2, 2026. Confirm the form, channel, requirements and deadline when filing. This article does not replace case-specific advice.
Request an Adjustment Notice Review to select 83/ISR or 84/ISR and close attachments, returns and evidence before submission.