The landscape of UK corporate compliance has officially shifted. As of March 31, 2026, the joint filing service that allowed UK Limited Companies to submit their annual accounts to Companies House and their Company Tax Return (CT600) to HMRC simultaneously has been decommissioned.
If you are a director or a business owner, the days of "one and done" submissions are over. You are now required to navigate two distinct digital workflows, each with its own technical requirements and portals. This change is part of a broader push toward digital transparency under the Economic Crime and Corporate Transparency Act 2023 and the ongoing expansion of Making Tax Digital (MTD).
At Sterlinx Global, we understand that these administrative shifts can feel like a distraction from your core business operations. This guide breaks down exactly what has changed, why it matters, and how you can ensure your business remains compliant in this new era of separate filing.
The New Reality: Two Submissions, Two Destinations
Previously, the "CASC" (Company Accounts and Tax Online) service provided a streamlined bridge between the two government departments. It was a convenient way for smaller entities to handle their end-of-year obligations in one sitting. However, that bridge has been dismantled.
Now, your compliance cycle looks like this:
- HMRC Filing: You must submit your CT600 Tax Return and accounts to HMRC using commercial software. The era of using basic HMRC-provided web forms for these submissions is ending, as HMRC mandates the use of iXBRL (Inline eXtensible Business Reporting Language) formatted files.
- Companies House Filing: Your annual accounts must be submitted directly to Companies House. While they offer a web filing service for some accounts, the long-term goal is to move all corporate entities toward software-only filing to improve data accuracy.
Failing to recognize these as two separate tasks is the fastest way to incur late filing penalties. You can no longer assume that hitting "submit" on one platform satisfies your obligations to the other.
Why the Joint Filing Service Ended
This isn't just a change for the sake of bureaucracy. The UK government is modernizing how corporate data is captured and verified. By separating the workflows, HMRC and Companies House can implement more robust checks and balances.
Enhanced Data Accuracy
By requiring commercial software, the government ensures that data is tagged correctly using iXBRL. This allows for automated analysis of company accounts, making it easier to spot inconsistencies or potential fraud. This move aligns with the standards we maintain when managing UK Limited Company accounting for our clients.
The Economic Crime and Corporate Transparency Act
A major driver of this change is the need for better corporate transparency. Companies House is transforming from a passive registrar to an active regulator. Separating the filing process allows them to implement new gatekeeping measures, such as identity verification for directors, which is rolling out throughout 2025 and 2026.
Identity Verification: The New 2026 Prerequisite
One of the most critical updates accompanying the end of joint filing is the mandatory identity verification for company directors and People with Significant Control (PSCs).
If you are filing accounts in 2026, you must ensure that the directors associated with the company have completed their identity checks with Companies House. Without this verification, you may find yourself unable to file accounts, or worse, facing criminal sanctions. This is a "hard" requirement: there are no workarounds.
What you need to do:
- Set up a Personal Tax Account or use the new Companies House identity verification service.
- Ensure all directors provide a valid form of ID (such as a passport or driving license).
- Complete this process well before your filing deadline to avoid a last-minute bottleneck.
The Technical Burden: Moving to iXBRL Commercial Software
HMRC now requires tax returns to be submitted in a specific digital format known as iXBRL. If you were previously relying on the joint service’s manual entry fields, you will now need to transition to compatible accounting software.
This transition isn't just about "getting software"; it’s about ensuring the software is correctly configured to tag every financial line item according to the latest UK GAAP or IFRS standards. For many SMEs, this technical hurdle is where the risk of error is highest.
If you are feeling overwhelmed by the technical requirements, remember that we provide a complete software service with DATEV to ensure your data is always formatted correctly for HMRC. Leveraging a specialized compliance partner ensures that your iXBRL tagging is accurate, reducing the risk of your return being rejected or flagged for manual review.
Avoid the New Points-Based Penalty System
Timeliness is more important than ever. Because you are now managing two separate deadlines and two separate platforms, the risk of "forgetting" one side of the equation has doubled.
HMRC has introduced a points-based penalty system for late submissions. Under this system, you don't just get a one-off fine; you accrue points for every missed deadline. Once you hit a certain threshold, a significant financial penalty is triggered. You can read more about how this works in our guide to HMRC's new points-based penalty system.
Common pitfalls to watch for:
- The "Submission Lag": Just because you filed with Companies House doesn't mean your HMRC accounts are ready. You need time to prepare the tax computations based on those accounts.
- Software Authentication: Many businesses find out on the day of the deadline that their software isn't "talking" to HMRC’s API, or their Government Gateway credentials have expired.
- Incomplete Data: Missing receipts or un-reconciled bank feeds will delay the production of accounts, making it impossible to file either document on time.
A 5-Step Checklist for Your 2026 Filing
To stay ahead of these changes, we recommend following this structured checklist. Don't wait until your year-end to start this process.
1. Audit Your Current Software
Does your current accounting software support direct filing to both Companies House and HMRC? If you are using spreadsheets or manual records, 2026 is the year you must migrate to a digital-first approach.
2. Verify Director Identities
Confirm that all directors and PSCs have completed their identity verification. If you have international directors, this process can take longer, so start immediately.
3. Update Your Internal Calendar
Mark two separate deadlines for your annual compliance. While the dates may be the same (usually 9 months after your year-end for accounts and 12 months for the tax return), treat them as two distinct projects. For more on avoiding common errors, see our post on 7 mistakes with 2026 HMRC updates.
4. Back Up Historical Joint Filings
Since the joint filing service is closed, you may lose easy access to historical documents submitted through that portal. Log in to your Government Gateway and download copies of all previous CT600s and accounts for your records.
5. Partner with a Compliance Expert
The most effective way to manage these changes is to delegate the entire process. At Sterlinx Global, we handle the end-to-end compliance delivery. You provide the data, and we ensure it is correctly tagged, filed, and verified across both HMRC and Companies House.
Frequently Asked Questions
Can I still file paper accounts?
While paper filing is technically possible for some companies at Companies House, it is highly discouraged and HMRC requires almost all companies to file their tax returns and accounts online. Moving to digital is the only way to ensure long-term compliance.
Do I need to pay twice for filing?
There is no "filing fee" for the HMRC tax return, but Companies House charges an annual fee for the confirmation statement (which is separate from the accounts). However, you will likely see an increase in software or service costs because you are now managing two distinct workflows.
Does this apply to dormant companies?
Yes. Even dormant companies have filing obligations. While the requirements are simpler, you still need to ensure you are using the correct separate filing routes for both organizations.
What happens if I miss the Companies House deadline but file with HMRC?
You will still be hit with an automatic late filing penalty from Companies House. The penalties range from £150 up to £1,500 depending on how late the accounts are. HMRC will also apply their own set of penalties for the missed tax return.
How Sterlinx Global Supports Your Transition
The end of joint filing is a clear signal that the UK government is tightening its grip on corporate data. Managing this transition alone can be time-consuming and risky.
Sterlinx Global operates as your dedicated compliance partner. We don't just give advice; we execute the work. From daily bookkeeping to year-end accounts and VAT filings, we manage the entire lifecycle of your company’s compliance. Whether you are a UK-based SME or an international business navigating cross-border VAT and UK tax, we provide the structured support you need to thrive.
Don't let a technical change in filing procedures lead to unnecessary fines and stress. Ensure your business is ready for the separate filing mandate today.
Need help with your 2026 filings? Talk to an expert at Sterlinx Global and let us handle the complexity for you.
