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Company Tax Return (CT600)
Outsourcing for UK Accountancy Practices
software, with iXBRL-tagged accounts and clear, review-ready tax schedules.
CT600s Prepared Right, First Time
Corporation Tax calculations require more than applying a single rate. Since April 2023, the rate has depended on a company’s profits, with marginal relief potentially applying between the small profits and main rate limits. Those limits are also reduced according to the number of associated companies, making the correct treatment of group structures an important part of the calculation.
Unison Globus supports UK accountancy practices with Corporation Tax computations and CT600 Company Tax Returns, prepared in your software with the supporting schedules and documentation your reviewers need for an efficient review and sign-off.
Corporation Tax computations prepared from your accounts, with supporting schedules and tax adjustments
Associated company positions and marginal relief assessed where applicable
Accounts and computations prepared or checked in iXBRL format, as required
Corporation Tax payment deadlines and amounts due set out for your client letter
Need Support with Company Tax Returns?
Keep UK Corporation Tax returns on track with reliable preparation support, clear fixed pricing and review-ready work.
✓ Fixed price agreed before work starts
✓ Clear scope and agreed turnaround
✓ Support with Company Tax Returns and CT600 preparation
✓ 10-hour free trial available
Get in Touch!
Our Company Tax Return Services - What We Handle for Your Firm
Corporate tax compliance from computation to filing pack. For the accounts themselves, see Year-End Accounts.
CT600 Preparation
- Company Tax Return preparation in your software
- iXBRL tagging of accounts and tax computations
- Supplementary pages, including CT600A and CT600L where applicable
- Short and long accounting period returns
- Dormant and micro-company returns
Tax Computations
- Adjustment of accounting profit to taxable profit
- Disallowable expenditure schedules
- Capital allowances, including AIA and writing-down allowances
- Loss utilisation, carry-back and carry-forward
- Interest and financing adjustments
Rates & Reliefs
- Small profits rate, main rate and marginal relief calculations
- Associated company reviews and limit apportionment
- Support with R&D tax relief claims and CT600L reporting, where applicable
- Patent Box and creative industry tax relief support
- Group relief computations
Director & Shareholder Items
- Directors’ loan accounts and Section 455 Corporation Tax charges
- Dividend and salary extraction schedules
- Benefits in kind cross-checked against P11D forms, where applicable
- Close company reviews
Payments & Deadlines
- Corporation Tax payment schedules with due dates
- Quarterly instalment payment reviews for larger companies
- Late filing and payment exposure flagged early
- Prior-year amendments where needed
Review Support
- Schedules cross-referenced to the accounts
- Prior-year comparisons and variance notes
- Consolidated query list per client
- Filing pack ready for your approval
Corporation Tax for 2026/27
Small Profits Rate 19%
Applies to eligible companies with profits up to £50,000.
Main Rate 25%
Applies to companies with profits above £250,000.
Marginal Relief
Companies with profits between £50,000 and £250,000 may qualify for Marginal Relief, reducing the effective rate of Corporation Tax.
Key Deadlines
Corporation Tax is payable 9 months and 1 day after the accounting period ends. The Company Tax Return (CT600) is due 12 months after the accounting period ends.
How Unison Globus Supports Company Tax Returns
With 20+ years of experience, Unison Globus supports Company Tax Return preparation to a consistent standard, so your reviewers can focus on judgement rather than data entry.
How We Work with Your Firm
- Dedicated tax preparers assigned to your client portfolio
- Tax computations reconciled to the accounts and fixed asset register
- Associated company and marginal relief checks, where applicable
- One consolidated query list per client
- Capacity planned around your clients’ Corporation Tax deadlines
Our CT600 Process
Receive
Collect the finalised accounts, trial balance, fixed asset register and prior-year tax computation.
Compute
Prepare the tax computation, including disallowable expenses, capital allowances, losses and reliefs.
Check Rates
Apply the correct Corporation Tax rate, check associated companies and calculate marginal relief where applicable.
Prepare CT600
Complete the return in your tax software and attach the iXBRL-tagged accounts and computation.
Deliver
Hand over the return, computation, payment schedule and query list for your review and filing.
How Our Delivery Model Works
When you partner with Unison Globus, you get a structured delivery model built around consistency, accountability and data security.
Structured Workflows and Execution
- Defined workflows and checklists for every task
- Standardised processes to ensure consistency across deliverables
- Timelines aligned with Corporation Tax payment and Company Tax Return filing deadlines
Dedicated Point of Contact
- Single point of contact for communication and coordination
- Direct access to your team during UK working hours (GMT/BST)
- Faster resolution of queries and updates
Regular Check-ins and Reporting
- Daily or weekly updates based on your preference
- Return status tracking across your corporate client list
- Scheduled review calls ahead of filing deadlines
Quality Control and Review Layers
- Multi-level review before final delivery
- Error tracking and continuous improvement
- Outputs aligned with your firm’s standards
Data Security and Compliance
- ISO 27001:2022 and ISO 27701:2019 certifications
- SOC 2 Type II assurance and UK GDPR-aligned processing, subject to the applicable scope
- Controlled, role-based access and secure data environments
Flexible and Scalable Team Support
- Scale team size based on workload
- Additional capacity around year-end and filing deadline peaks
- Continuity maintained as capacity changes
Aligned Tools and Working Environment
- Work within TaxCalc, IRIS, CCH, Capium or your existing tax software
- Follow your formats, templates and documentation style
Hire Dedicated Corporate Tax Staff in India
Add trained corporate tax preparers who work in your software, follow your review standards and scale with your year-end workloads.
Flexible Resourcing Models
Full-Time Tax Preparation Support
- 8 hours per day, aligned with your UK working hours
- Integrated into your existing workflows and review procedures
- Suitable for firms with a consistent, year-round Company Tax Return workload
Part-Time Tax Preparation Support
- Flexible working hours based on your workload
- Suitable for practices that need additional preparation capacity
- Additional support during peak tax periods, subject to availability
Prepaid Block of Hours
- Minimum purchase of 50 hours at £18.50 per hour
- Payment upfront, with no expiry on purchased hours
- Use your hours as required to manage changing workloads
Not sure which model fits? Start with a 10-hour free trial.
Book 10-Hour Free TrialHow Unison Globus Supports Company Tax Returns
With 20+ years of experience, Unison Globus supports Company Tax Return preparation to a consistent standard, so your reviewers can focus on judgement rather than data entry.
How We Work with Your Firm
- Dedicated tax preparers assigned to your client portfolio
- Tax computations reconciled to the accounts and fixed asset register
- Associated company and marginal relief checks, where applicable
- One consolidated query list per client
- Capacity planned around your clients’ Corporation Tax deadlines
Who Our Services Are For
Practices with large limited company portfolios
Firms handling groups and associated companies
Practices managing 31 March and 31 December year-end workloads
Firms wanting review-ready computations rather than raw drafts
Software Landscape
Explore Our Other Services
As your practice grows, your requirements often go beyond this service. Unison Globus supports UK firms across additional areas to ensure continuity and control.
Year-End Accounts
FRS 102 / FRS 105 statutory accounts with iXBRL filing to Companies House.
Tax Preparation
The full range of personal, business and corporate tax compliance.
Company Secretarial Services
Confirmation statements, Companies House filings and identity verification support.
VAT Services
VAT returns, scheme handling and MTD for VAT submissions.
Audit & Assurance Support
Audit preparation, documentation and working papers.
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FAQs
The small profits rate is 19% for taxable profits up to £50,000, and the main rate is 25% for profits over £250,000. Marginal relief applies between these limits.
Marginal relief reduces Corporation Tax for profits between the lower and upper limits, with the effective rate increasing from 19% towards 25%. The standard marginal relief fraction is 3/200.
The £50,000 and £250,000 limits are divided by the total number of associated companies, including the company itself. This can mean a company reaches the main rate at a lower profit level. We check the position on every job.
Payment is normally due 9 months and 1 day after the end of the accounting period, and the CT600 is due 12 months after the period ends. Companies meeting the relevant criteria must pay by quarterly instalments.
Yes. We tag the accounts and computation and prepare the complete filing pack for your approval.
We support the computation and CT600L preparation. The claim methodology and sign-off stay with your firm.
We prepare the return for your review and approval. Submission is normally made by your practice as the authorised agent.
Onboarding is typically completed within days of finalising requirements.
Get Company Tax Returns Off Your Bottleneck List
Whether you need ongoing CT600 capacity or help clearing a backlog before a filing deadline, Unison Globus prepares work to a standard your reviewers can sign off quickly.
- Discuss your company tax portfolio
- Choose the right support model
- Start with a 10-hour free trial
