When is the ICSOE return due?

Every four months, no later than 17 January, 17 May and 17 September (Social Security Law, Article 15 A, third paragraph). Each return covers the previous four-month period: January-April, May-August and September-December (IMSS Guidelines, point 5.4). If the 17th falls on a Saturday, Sunday or public holiday, the deadline moves to the next working day (point 5.5).

Do I have to file if I signed no contracts in the period?

Yes. In that case a "Sin Información" (no information) return is filed (Guidelines, point 5.6).

What happens if I file late?

Filing the Article 15 A information after the legal deadline is an infringement punishable by a fine (Social Security Law, Articles 304 A, section XXII, and 304 B, section V). No fine applies if the late filing is spontaneous, that is, before the Institute discovers the omission or notifies a demand or visit order (Article 304 C).

Can I correct a return already filed?

Yes. There are supplementary returns for correction (replaces the previous one), cancellation (removes a return or reverses a "Sin Información" return) and update (reports later changes to the contracts). Up to 4 supplementary returns are allowed per period, except update returns (Guidelines, point 5.6).

Does the client company have to do anything?

The filing obligation is the contractor's, but the client is jointly liable for the workers if the contractor fails to meet its social security obligations (Social Security Law, Article 15 A, second paragraph). It can ask the contractor to authorise it, via Buzón IMSS, to view the detailed information on the reported contracts (Guidelines, point 7.1), and can check the IMSS public list (point 6.1).

MX · Expiry & renewal tracking

Never file an ICSOE report late

Providers of specialised services or works in Mexico report each four-month period's contracts to IMSS through the ICSOE system by 17 January, 17 May and 17 September, even with no contracts (Social Security Law, Article 15 A). Filing late or not at all is an offence punished with a fine (Articles 304 A and 304 B).

Any individual or company that provides specialised services or carries out specialised works in Mexico must give the Mexican Social Security Institute (IMSS), every four months and no later than the 17th of January, May and September, the information on the contracts signed in that four-month period: details of the parties (name or company name, RFC tax ID, address, email and phone), details of each contract (purpose, period of validity, list of workers with name, CURP, social security number and contribution base salary, and the client's name and RFC) and a simple copy of the registration issued by the Ministry of Labour and Social Welfare (Social Security Law, Article 15 A, third paragraph, sections I to III).

The information is filed through the ICSOE system (Informativa de Contratos de Servicios u Obras Especializados), which IMSS runs, and the return is signed with the SAT e.firma (General Guidelines for compliance with the third paragraph of Article 15 A, published in the DOF on 13 April 2022, points 4.1 and 4.2). The deadlines are: first period (January to April), 1 to 17 May; second (May to August), 1 to 17 September; third (September to December), 1 to 17 January of the following year. If the last day falls on a Saturday, Sunday or public holiday, the deadline moves to the next working day (points 5.4 and 5.5).

Even if no contracts were signed in the period, a "Sin Información" (no information) return must be filed (point 5.6). For every return the system issues an electronic acknowledgement that proves the date and time of receipt (point 5.7). IMSS publishes on its website, and updates at least monthly, a public list of the contracts reported (points 6.1 and 6.2).

The client company has a stake in compliance too: anyone who contracts services or works with a provider that fails to meet its social security obligations is jointly liable for the workers used (Social Security Law, Article 15 A, second paragraph), and may only subcontract specialised services or works with contractors listed in the STPS register (Federal Labour Law, Article 13).

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At a glance

Who files it	The individual or company providing specialised services or carrying out specialised works (Social Security Law, Article 15 A, third paragraph)
Frequency	Every four months: no later than 17 January, 17 May and 17 September (Article 15 A; Guidelines, point 5.4)
Period covered by each return	January-April (filed 1 to 17 May), May-August (1 to 17 September) and September-December (1 to 17 January of the next year) (Guidelines, point 5.4)
If the 17th is not a working day	The deadline moves to the next working day (Guidelines, point 5.5)
No contracts in the period	A "Sin Información" return must still be filed (Guidelines, point 5.6)
Channel and signature	IMSS ICSOE system, signed with the SAT e.firma; the system issues an acknowledgement (Guidelines, points 4.1, 4.2, 5.1 and 5.7)
Attachment	Simple copy of the REPSE registration issued by the STPS (Social Security Law, Article 15 A, section III)

Who is responsible?

The contractor (the specialised-service provider or specialised-works contractor) is responsible for filing correct and complete information with IMSS through ICSOE (Guidelines, point 5.9). It may authorise the client company, through the Buzón IMSS, to view the detailed information on the contracts between them (points 7.1 and 7.2). The client, in turn, is jointly liable if the contractor fails to meet its social security obligations (Social Security Law, Article 15 A, second paragraph).

If the deadline passes

Failing to file, or filing after the legal deadline, the information required by Article 15 A is an infringement (Social Security Law, Article 304 A, section XXII) punishable by a fine (Article 304 B, section V). No fine is imposed when the obligation is met spontaneously after the deadline, unless the omission was discovered by the Institute or corrected after a visit order or demand was notified (Article 304 C). If IMSS finds errors in what was reported, it may ask by email for a correction within the following 10 working days (Guidelines, point 8.1), and where information was not reported or differs from what third parties reported it grants 15 working days to correct or clarify (point 10.2).

Three fixed dates a year, not an expiry date

Unlike a licence, the ICSOE return does not "expire": it has three fixed deadlines each year (17 May, 17 September and 17 January). Besides the normal return, update returns are filed in May, September and January, while correction and cancellation returns can be filed at any time (Guidelines, points 5.6 and 5.9). That is why it is best to record the next filing deadline in ExpirySuite and, once filed, move it to the next period.

Tracking it with ExpirySuite

Add a record for each contractor that must file (your own company, if you provide specialised services) and enter the next filing deadline as the expiry date: 17 May, 17 September or 17 January. When the return is filed, move the date to the next four-month period.
Email reminders arrive 60, 30, 14, 7 and 1 day before the deadline and on the day; the 30-day reminder roughly coincides with the start of the signing window (the 1st to the 17th of the month).
The contractor or your payroll team can upload the electronic acknowledgement through a secure link that is valid for 14 days and needs no account.
Assign a responsible person, such as payroll or compliance; if the deadline passes with no acknowledgement, managers get further reminders 3, 7 and 14 days later.

Frequently asked questions

When is the ICSOE return due?: Every four months, no later than 17 January, 17 May and 17 September (Social Security Law, Article 15 A, third paragraph). Each return covers the previous four-month period: January-April, May-August and September-December (IMSS Guidelines, point 5.4). If the 17th falls on a Saturday, Sunday or public holiday, the deadline moves to the next working day (point 5.5).
Do I have to file if I signed no contracts in the period?: Yes. In that case a "Sin Información" (no information) return is filed (Guidelines, point 5.6).
What happens if I file late?: Filing the Article 15 A information after the legal deadline is an infringement punishable by a fine (Social Security Law, Articles 304 A, section XXII, and 304 B, section V). No fine applies if the late filing is spontaneous, that is, before the Institute discovers the omission or notifies a demand or visit order (Article 304 C).
Can I correct a return already filed?: Yes. There are supplementary returns for correction (replaces the previous one), cancellation (removes a return or reverses a "Sin Información" return) and update (reports later changes to the contracts). Up to 4 supplementary returns are allowed per period, except update returns (Guidelines, point 5.6).
Does the client company have to do anything?: The filing obligation is the contractor's, but the client is jointly liable for the workers if the contractor fails to meet its social security obligations (Social Security Law, Article 15 A, second paragraph). It can ask the contractor to authorise it, via Buzón IMSS, to view the detailed information on the reported contracts (Guidelines, point 7.1), and can check the IMSS public list (point 6.1).

Sources

Last checked: Oct 10, 2026 · This page summarises official sources for general information and is not legal advice. Check the linked sources for current rules and fees.

Made for four-monthly specialised-services contract report to IMSS (ICSOE) (Mexico)

A ready template for four-monthly specialised-services contract report to IMSS (ICSOE) (Mexico) with sensible validity defaults, so you enter less and track more.

Reminders on time

Email alerts at 60, 30, 14, 7 and 1 day before each four-monthly specialised-services contract report to IMSS (ICSOE) (Mexico) expires, plus overdue escalation to managers.

Assign an owner

Give each four-monthly specialised-services contract report to IMSS (ICSOE) (Mexico) an owner and let employees update their own via a secure link — no login needed.