CSSF Reporting Calendar Q3 2026: Deadlines and Submissions for Luxembourg Firms

ByOfficer

Last updated: May 2026

Q3 looks quieter than Q2 on paper. No CRS or FATCA annual filings, no annual accounts deadline, no cluster of tax and prudential deadlines landing in the same week. That surface calm misleads reporting teams every year. The Q2 reference date (30 June 2026) triggers the full suite of quarterly prudential filings in August, right when half the team is on leave. And August is the month where the CSSF reporting calendar Q3 2026 actually gets dense.

I have seen more late COREP submissions in August than in any other month. The pattern is consistent: the 11 August SI deadline falls mid-vacation, backup signatories are unavailable, and the one person who knows the eRIIS upload process is unreachable. The solution is simple but teams skip it. Move the internal review window forward into July, treat August as execution-only, and confirm portal access before anyone leaves.

This article covers every reporting obligation due between July and September 2026 for credit institutions and fund managers supervised by the CSSF. It builds on the Q2 2026 reporting calendar, which covered April through June. Where Q2 focused on CRS/FATCA, annual accounts, and Q1 prudential filings, Q3 shifts to Q2 prudential remittances, AIFMD Annex IV quarterly filings, CESOP, and the UCITS semi-annual reporting window.

Related reading: COREP Reporting Explained

How to Use the CSSF Reporting Calendar Q3 2026

Deadlines are grouped by month, then by entity type: credit institutions first, then fund managers, then obligations that apply across entity types. Where a deadline falls on a weekend or Luxembourg public holiday, the standard EBA convention is to shift to the next business day. The BCL follows a similar approach for statistical returns. Confirm the convention with each authority individually if a borderline case arises.

Each entry includes the framework, reference period, submission channel where known, and the legal or regulatory basis. The Q2 calendar covered reporting channels in detail. This article does not repeat that section in full but flags channel-specific issues where Q3 introduces a wrinkle.

One operational note that matters for Q3 specifically: the 15 August public holiday (Assumption) falls on a Saturday in 2026. It is also the 15th-calendar-day date for the 31 July monthly LCR and monthly ALMM submissions under the CSSF reporting requirements. Under the standard EBA convention, the remittance shifts to the next business day, Monday 17 August 2026. Set the internal upload target before the holiday weekend regardless, and confirm the handling with your reporting portal.

July 2026

Credit Institutions

July is dominated by monthly recurring submissions. No quarterly prudential filings are due this month.

Monthly LCR (reference date: 30 June 2026). The CSSF reporting requirements list LCR templates C 72.00 to C 76.00 with a deadline of the 15th calendar day after the reporting reference date. The June reference date submission is therefore due on 15 July 2026 (Wednesday), not 30 July.

Monthly ALMM (Additional Liquidity Monitoring Metrics, reference date: 30 June 2026). The CSSF reporting requirements apply the same 15th-calendar-day deadline to monthly ALMM templates. The June reference date monthly ALMM submission is due on 15 July 2026. Where a specific ALMM template is reported quarterly under the proportionality conditions in the ITS, the Q2 deadline follows the quarterly schedule and falls on 11 August 2026.

BCL statistical reporting (reference date: June 2026). The Banque Centrale du Luxembourg requires monthly balance sheet statistics (BSI reporting) from all monetary financial institutions. The typical deadline is the 15th business day after month-end, which lands around 22 July 2026. Submission is through the BCL S3 portal (Collecte Statistique).

The trap I see in July: teams treat it as a “quiet month” because the quarterly prudential deadline is in August. But July is when Q2 COREP and FINREP data extraction should start. The 30 June reference date means the half-year close data needs to be reconciled and loaded into reporting templates during July. If your institution has a December year-end, the H1 close process and the Q2 prudential data pull run in parallel. Departments that do not coordinate these two workflows find themselves scrambling in August when both the COREP deadline and the half-year management accounts review converge.

Fund Managers

AIFMD Annex IV reporting (Q2 2026, quarterly reporters). Under Article 110 of the AIFMD Delegated Regulation (EU) No 231/2013 and CSSF Circular 18/698, AIFMs reporting quarterly must submit their Annex IV data within 30 calendar days of the quarter-end. For Q2 2026 (reference date 30 June), the deadline is 30 July 2026 (Thursday). Submission through the CSSF eRIIS portal.

Semi-annual AIFMD Annex IV (reference date: 30 June 2026). AIFMs on a semi-annual reporting frequency (those whose total assets under management are above EUR 100 million but do not exceed EUR 500 million for leveraged portfolios, or above EUR 500 million but do not exceed EUR 1 billion for unleveraged portfolios) must also file by 30 July 2026. The 30-day window from the semi-annual reference date is the same as for quarterly reporters. The difference is these firms only file twice per year instead of four times. If you switched AuM threshold bands since the last filing, verify your frequency classification with the CSSF before submitting.

UCI monthly reporting (O 1.1 tables). Management companies and self-managed SICAVs submit monthly net asset data to the CSSF. The standard deadline is 20 calendar days after month-end. For the June reference period, that is around 20 July 2026 (Monday).

AIFMD II transposition. Directive (EU) 2024/927 (AIFMD II) required Member State transposition by 16 April 2026. Luxembourg has transposed the directive (Bill 8628), with the new requirements applying from 16 April 2026. The changes affect liquidity management tool requirements, delegation arrangements, loan-originating AIF rules, and Annex IV reporting content. The reporting impact will not be immediate for Q2 2026 filings (the enhanced supervisory reporting requirements under AIFMD II apply only from 16 April 2027 and depend on updated ESMA-level technical standards), but fund managers should be mapping the new requirements. Where ESMA has not yet published updated reporting templates, the existing Annex IV framework continues to apply. The risk is assuming that AIFMD II means an immediate overhaul of the Annex IV submission. It does not, but the governance and risk management changes are live from transposition.

All Entities

CESOP (Central Electronic System of Payment Information). Payment service providers, including e-money institutions operating in Luxembourg, must file quarterly CESOP reports. The Q2 2026 report (covering April to June) is due by 31 July 2026 (Friday). This covers cross-border payment data exceeding 25 transactions per payee per quarter. Filed through the Luxembourg tax authority portal.

EMIR trade reporting. Daily and ongoing. No Q3-specific deadline, but July is when ESMA publishes its annual data quality report covering the prior year. If your pairing and matching rates were below threshold in 2025, expect outreach from your trade repository or the CSSF during Q3.

August 2026

Credit Institutions

August is the heavy month. The Q2 reference date (30 June 2026) drives the quarterly prudential cluster.

Quarterly COREP Own Funds (C 01.00 to C 06.02) and COREP Credit Risk (C 07.00 to C 14.01). The CSSF reporting requirements list the Q2 quarterly remittance date as 11 August 2026 (Tuesday). This is the hard deadline to plan around for the Q2 prudential package.

Quarterly FINREP (F 01.01 to F 46.00). Same 11 August 2026 deadline as COREP. The Q2 FINREP submission includes the half-year P&L (templates F 02.00 and F 03.00), which means it must reconcile with the H1 2026 management accounts. This is where teams run into the same problem flagged in the Q2 calendar: if the H1 close is not finalised by early August, the FINREP submission may rely on preliminary figures. The CSSF does not publish a formal materiality threshold for triggering a resubmission, so your internal policy needs to define what constitutes a material variance between preliminary and final H1 numbers.

The Q2 FINREP carries an additional complication that Q1 does not. The half-year point is when impairment models (IFRS 9 ECL) are typically recalibrated. If your institution runs a full staging reassessment at H1, the ECL impact flows through FINREP templates F 12.00 and F 12.01. Late staging adjustments that arrive after the FINREP submission create a reconciliation problem. I have handled situations where the risk team finalised staging moves a week after the COREP deadline, requiring a FINREP resubmission because the ECL shift was material enough to affect capital ratios.

Quarterly Large Exposures (C 26.00 to C 31.00). Same 11 August 2026 deadline. The LE templates track the COREP remittance cycle. For Q2, cross-check any client group restructurings that occurred during H1 against your connected-client mapping. The connected-client review that most institutions run at year-end sometimes misses mid-year changes. If a corporate client reorganised its group structure in Q2, your LE filing must reflect the updated grouping.

Quarterly NSFR (C 80.00 to C 84.00). Due alongside COREP on 11 August 2026 for SIs. NSFR is quarterly, unlike the monthly LCR. The common classification error remains the treatment of operational deposits. The NSFR available stable funding (ASF) factor for operational deposits differs from the LCR treatment of the same balances. Teams that carry forward LCR bucket assignments into NSFR without adjusting for the longer time horizon will generate validation warnings.

MREL reporting (M 01.00 to M 07.00). Quarterly, reference date 30 June 2026. The remittance period under the ITS on MREL reporting is approximately 49 calendar days. That puts the deadline around 18 August 2026 (Tuesday). File through the SRB reporting channel for entities under SRB resolution planning, or through the CSSF for entities under national resolution authority scope. As noted in the Q2 calendar, the SRB and CSSF do not automatically share your MREL data. Confirm which authority you report to and file to the correct channel.

Monthly LCR (reference date: 31 July 2026). The CSSF deadline is the 15th calendar day after the reporting reference date, so the published calendar-day date is 15 August 2026 (Saturday, Assumption). Because this is both a weekend and a Luxembourg public holiday, the remittance shifts to the next business day, Monday 17 August 2026, under the standard EBA convention. Set your internal upload target before the holiday weekend regardless, and confirm the handling with your reporting portal.

Monthly ALMM (reference date: 31 July 2026). The same 15th-calendar-day rule applies to monthly ALMM templates, giving a published calendar-day date of 15 August 2026. Quarterly ALMM templates, where applicable under the proportionality conditions, follow the Q2 quarterly deadline of 11 August 2026.

BCL statistical reporting (reference date: July 2026). Due around 21 August 2026 (15th business day).

Fund Managers

UCITS semi-annual reports (January to June 2026 period). Under the Law of 17 December 2010, UCITS must publish their semi-annual report within two months of the period-end. For funds with a December year-end, the semi-annual period runs January to June 2026. The publication and CSSF filing deadline is 31 August 2026 (Monday). Management companies often prioritise the Annex IV deadline in July and defer the semi-annual report preparation, which compresses the August window. If your fund administrator delivers the NAV reconciliation late, the semi-annual report timeline tightens quickly.

UCI monthly reporting (O 1.1 tables). July reference date, due around 20 August 2026.

All Entities

MiFIR transaction reporting. Daily and ongoing under Article 26 of MiFIR (Regulation (EU) No 600/2014). No Q3-specific deadline shift. However, August is when many institutions run their mid-year reconciliation of MiFIR submissions against internal trade records. If your ARM (Approved Reporting Mechanism) flagged elevated rejection rates in H1 2026, resolve them before the CSSF’s annual data quality review cycle, which typically runs in Q4.

SFTR (Securities Financing Transactions Regulation). Daily reporting, ongoing under Regulation (EU) 2015/2365. No Q3-specific deadline. But August holiday periods historically produce a spike in late or missing SFTR submissions because backup staff lack familiarity with the daily reporting workflow. Ensure at least two trained operators are available throughout August.

September 2026

Credit Institutions

Monthly LCR (reference date: 31 August 2026). The CSSF deadline is the 15th calendar day after the reporting reference date. The August reference date submission is due on 15 September 2026 (Tuesday).

Monthly ALMM (reference date: 31 August 2026). Monthly ALMM follows the same 15th-calendar-day rule, so the August reference date submission is due on 15 September 2026.

BCL statistical reporting (reference date: August 2026). Due around 22 September 2026.

Semi-annual Pillar 3 disclosures. Large institutions and institutions listed on regulated markets must publish semi-annual Pillar 3 disclosures under CRR Article 433a and 433c. The H1 2026 reference date (30 June) means these disclosures should accompany or closely follow the half-year financial statements. For most Luxembourg banks publishing H1 results in September, the Pillar 3 semi-annual update should be published concurrently. The scope of the semi-annual disclosure is narrower than the annual version: it covers key metrics (KM1), own funds composition, and risk-weighted exposure amounts, but not the full set of annual templates.

A common error: treating the semi-annual Pillar 3 as optional because “only the annual one matters.” Under CRR Article 433a, large institutions must disclose on a semi-annual basis. The CSSF has not historically enforced this with the same intensity as prudential filing deadlines, but the EBA’s Pillar 3 assessment reports increasingly flag gaps in semi-annual disclosure timeliness.

Fund Managers

September is relatively light for fund manager filings. UCI monthly reporting for the August reference date is due around 20 September. No major quarterly AIFMD or UCITS deadline falls in September.

However, September is when fund managers should begin preparing for the Q3 AIFMD Annex IV filing (reference date 30 September, due 30 October). Quarterly reporters with complex AIF structures need to start the data collection process early, particularly for leverage calculations under the commitment and gross methods. I have seen firms where the leverage calculation alone takes three weeks because it requires consolidating derivative notional values across multiple sub-custodians and prime brokers. Starting in October for an October deadline does not work for these structures.

All Entities

DORA Register of Information. Under Article 28(3) of DORA (Regulation (EU) 2022/2554), financial entities must maintain an up-to-date register of all ICT third-party service arrangements. The CSSF collected the first registers of information from financial entities in April 2025 (reference date 31 March 2025) and now runs an annual cycle, transmitting consolidated registers to the ESAs by 31 March each year based on a 31 December reference date; the 2026 submission therefore used a 31 December 2025 reference date. By Q3 2026, the register is a living document. Any new ICT contracts signed, renewed, or terminated in Q2 or Q3 must be reflected. The ESAs may request an updated register at any time. Use September to reconcile Q2 and Q3 contract changes before the year-end update cycle begins.

DAC6 (Mandatory Disclosure Rules). DAC6 has no quarterly deadline. The 30-day reporting trigger runs continuously. But September is when many firms conduct their Q3 compliance review to verify that no reportable cross-border arrangements were missed during the summer months. Summer-period transactions are the ones most frequently missed because deal teams close structures in July or August without flagging them for DAC6 review.

Public Holidays That Affect Q3 Deadlines

Luxembourg has one public holiday in Q3 2026:

  • 15 August 2026 (Assumption). Falls on a Saturday. It does not affect the 11 August COREP/FINREP deadline, but it coincides with the CSSF 15th-calendar-day deadline for the 31 July monthly LCR and monthly ALMM reports. For those liquidity templates, the remittance shifts to Monday 17 August 2026 under the standard EBA convention. Set the internal upload target no later than Friday 14 August. Teams commonly take the full week of 10 to 14 August as leave, so the COREP sign-off window should still close the week before (3 to 7 August).

No other Luxembourg public holidays fall within Q3 2026. This makes the quarter operationally cleaner than Q2 (which had Labour Day, Ascension, Whit Monday, and National Day). The only scheduling pressure is the August leave period.

What Changed Since Q2 2026

Several regulatory developments from Q2 affect Q3 reporting or preparation.

AIFMD II Transposition

Directive (EU) 2024/927 (AIFMD II) required Member State transposition by 16 April 2026. The directive introduces new requirements for liquidity management tools, delegation oversight, loan-originating AIF frameworks, and expanded Annex IV reporting fields. The Annex IV reporting changes depend on ESMA’s updated implementing technical standards, which may not align precisely with the transposition date. For Q3 2026 Annex IV filings, continue using the existing template structure unless ESMA has published updated XML schemas and the CSSF has confirmed the go-live date for the new fields. The governance and risk management requirements, however, are live from the transposition date and should be reflected in your compliance framework even if the reporting templates have not caught up.

CRR3 Implementation: Second Year

CRR3 (Regulation (EU) 2024/1623) took effect on 1 January 2025. The Q2 2026 COREP submission (due August) is the sixth quarterly filing under the revised framework. The CSSF indicated in Q2 2026 that it would increase data quality scrutiny on CRR3-affected templates, particularly the output floor calculation (template C 02.00) and the revised credit risk standardised approach (C 07.00 series). By Q3, you should not be experiencing first-time implementation errors. If your Q1 or Q2 validation rule failures on output floor or credit risk templates remain unresolved, expect direct CSSF follow-up during the Q3 submission cycle.

EBA Framework 4.3 Taxonomy

The EBA’s reporting framework 4.3 introduces changes to third-country branch (TCB) reporting templates and AML reporting. The broader CRR3/CRD6 step 2 amendments (covering COREP own funds, FINREP/IFRS 18, FRTB, ALMM, and benchmarking) are planned under framework 4.4. For Q3 2026 filings, the reporting taxonomy remains on framework 4.2. Framework 4.3 introduces only new third-country branch and AMLA modules (first reference dates 31 March 2027 and 31 December 2026), so it does not change COREP or FINREP for Q3 2026. Monitor the EBA 4.3 draft technical package updates for confirmation of first reference dates.

DORA Enforcement Posture

DORA has been fully applicable since 17 January 2025. The CSSF collected the first registers of information in April 2025, and the 2026 annual submission used a 31 December 2025 reference date. By Q3, the supervisory posture is expected to shift from collection to review. If the CSSF identifies gaps in your register, they will communicate through the standard supervisory dialogue channel. Entities that submitted a register in the most recent annual cycle should not assume silence means acceptance. The review cycle takes time.

Building a Q3 Schedule That Survives August

The single biggest operational risk in Q3 is the August leave period colliding with the quarterly prudential deadline. Here is how to structure the quarter.

First two weeks of July: begin Q2 COREP/FINREP data extraction. Pull 30 June reference date trial balances, reconcile against ledger, start populating templates. Confirm all eRIIS, CASPER, and SRB portal credentials are current. Verify that at least two people can upload to each reporting channel. File the June reference date monthly LCR and monthly ALMM by 15 July, and prepare the AIFMD Annex IV filing due by 30 July.

Last two weeks of July: complete first-pass template population for COREP and FINREP. Run EBA validation rules locally. Identify any data quality issues that require source system investigation. File CESOP Q2 by 31 July. Begin UCITS semi-annual report preparation.

First week of August: internal review and sign-off of COREP/FINREP templates. Resolve validation errors. Cross-check NSFR against LCR to ensure consistent liability categorisation. Confirm Large Exposures connected-client mappings reflect any Q2 restructurings. Finalize MREL data.

Week of 10 August: submit COREP, FINREP, Large Exposures, NSFR, and any quarterly ALMM templates by 11 August. Submit the July reference date monthly LCR and monthly ALMM by the CSSF 15th-calendar-day deadline, with an internal target before the 15 August weekend. Submit MREL by 18 August. File UCITS semi-annual reports by 31 August.

September: file the August reference date monthly LCR and monthly ALMM submissions by 15 September. Reconcile the DORA register of information. Begin Q3 AIFMD Annex IV data collection for October filing. Run the DAC6 Q3 compliance review. Prepare semi-annual Pillar 3 disclosures.

The critical decision: who is available during the week of 10 August. Lock in the names in July. If both your COREP reviewer and your eRIIS uploader are on leave that week, you will file late. This is not a theoretical risk. It happens every August.

Frequently Asked Questions

Does the 15 August public holiday affect the COREP deadline?

No. The COREP/FINREP deadline for SIs is 11 August 2026, which is a Tuesday. The 15 August public holiday falls on a Saturday in 2026, so no deadline shift is triggered. The operational impact is indirect: many teams take the full week of 10 to 14 August as leave, compressing the final review window. Plan accordingly.

Are Q2 2026 AIFMD Annex IV filings affected by AIFMD II?

Luxembourg has transposed AIFMD II through Bill 8628, with the new governance and liquidity management requirements applying from 16 April 2026. The enhanced supervisory reporting requirements apply only from 16 April 2027 and depend on updated ESMA-level technical standards. Until ESMA publishes updated XML schemas and the CSSF confirms the go-live date for revised fields, the Q2 2026 Annex IV filing uses the existing template structure.

What is the MREL deadline for Q2 2026?

Approximately 18 August 2026. The MREL ITS sets the remittance at roughly 49 calendar days from the reference date (30 June). File through the SRB reporting channel if your institution is under SRB resolution planning, or through the CSSF if under national resolution authority scope.

What is the monthly LCR and ALMM deadline?

The CSSF reporting requirements state the deadline as the 15th calendar day after the reporting reference date for monthly LCR and monthly ALMM templates. For Q3 2026 operations, that means 15 July for the 30 June reference date, 15 August for the 31 July reference date, and 15 September for the 31 August reference date. If the 15th falls on a weekend or public holiday, confirm the portal handling with the CSSF and set an earlier internal upload target.

Is the UCITS semi-annual report due in August?

For UCITS with a December year-end, yes. The semi-annual period covers January to June 2026, and the publication deadline is two months after the period-end: 31 August 2026. This applies to both the publication obligation and the CSSF filing. Do not delay the filing because the fund administrator has not yet delivered the final version. File what you have by the deadline and update if needed.

Do I need to update my DORA register of information in Q3?

Yes. The register is a living document under Article 28(3) of DORA. Any new, renewed, or terminated ICT third-party contracts since your last register submission must be reflected. The CSSF or ESAs can request the register at any time. Use Q3 to reconcile against Q2 contract changes rather than waiting for a year-end bulk update.

What CESOP deadline falls in Q3?

The Q2 2026 CESOP report (covering April to June cross-border payment data) is due by 31 July 2026. Filed through the Luxembourg tax authority portal. The threshold remains 25 transactions per payee per quarter.

Key Takeaways

  • The Q2 2026 COREP/FINREP deadline is 11 August 2026. Move internal review into July so that August is execution-only.
  • AIFMD Annex IV for quarterly and semi-annual reporters is due 30 July 2026. Semi-annual reporters filing for the first time at H1 should verify their frequency classification.
  • MREL quarterly filing is due around 18 August 2026. Confirm your filing authority (SRB or CSSF) before submission.
  • UCITS semi-annual reports (January to June 2026) for December year-end funds are due by 31 August 2026.
  • Monthly LCR and monthly ALMM are due on the 15th calendar day after the reporting reference date, not on a 30-day cycle. Q3 operating dates are 15 July, 15 August, and 15 September for the June, July, and August reference dates.
  • The 15 August public holiday falls on a Saturday and coincides with the July reference date monthly LCR and ALMM calendar-day deadline. Set an earlier internal upload target.
  • DORA register maintenance is ongoing. Reconcile Q2/Q3 ICT contract changes before year-end.
  • AIFMD II governance requirements apply from 16 April 2026 following Luxembourg transposition, while enhanced supervisory reporting requirements apply from 16 April 2027 and depend on updated ESMA technical standards.

Related Articles

Sources and References

  • CSSF Reporting requirements for credit institutions – CSSF
  • Commission Implementing Regulation (EU) 2024/3117 on supervisory reporting (ITS on reporting) – EUR-Lex
  • Regulation (EU) No 575/2013 (CRR) as amended by Regulation (EU) 2024/1623 (CRR3) – EUR-Lex
  • Directive 2011/61/EU (AIFMD) and Commission Delegated Regulation (EU) No 231/2013 – EUR-Lex
  • Directive (EU) 2024/927 (AIFMD II) – EUR-Lex
  • Regulation (EU) 2022/2554 (DORA) – EUR-Lex
  • Regulation (EU) No 600/2014 (MiFIR) – EUR-Lex
  • Regulation (EU) 2015/2365 (SFTR) – EUR-Lex
  • Commission Implementing Regulation (EU) 2021/763 (ITS on reporting and disclosure of MREL and TLAC) – EUR-Lex
  • CSSF Circular 18/698 (AIFMD reporting) – CSSF
  • Law of 17 December 2010 (Luxembourg UCITS law) – Legilux
  • Council Directive (EU) 2020/284 on CESOP – EUR-Lex
  • Council Directive (EU) 2018/822 (DAC6) and Luxembourg Law of 25 March 2020 – EUR-Lex

Disclaimer: The information on RegReportingDesk.com is for educational and informational purposes only. It does not constitute legal, regulatory, tax, or compliance advice. Always consult your compliance officer, legal counsel, or the relevant supervisory authority for guidance specific to your institution.

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