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Self-Employed Individuals & Sole Traders
Advice and assistance in preparing tax returns for sole traders and self-employed clients that have business income, allowable expenses and relevant tax deductions.
Outsourced Self Assessment Tax Return Services for UK Accounting Firms
Aone Outsourcing UK provides white-label Self Assessment tax return services to UK accounting firms and practices. We help accounting firms and practices prepare SA100 tax returns and review tax calculations so that they can manage heavy workloads without expanding their team.
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UK-focused
Built for accounting firms and practices
White-label
Your practice remains client-facing
Scalable
Increase or reduce support with workload
Review-ready
Draft returns, workings and flagged queries
Self Assessment support for accounting practices
Self-Assessment Tax Return Support for Accounting Practices
For accounting firms and accountancy practices, preparing Self Assessment tax returns for multiple clients takes time, especially during tax season. Maintaining accurate records, finding missing information, and checking tax calculations require time and attention.
Aone Outsourcing offers outsourced Self Assessment tax return preparation services to accounting firms and accounting practices in the UK as per HMRC regulations. We handle recurring tasks such as organising client data, drafting SA100 returns, creating the necessary return sections, checking calculations, and flagging missing or questionable information for clarification.
Whether your accounting practice needs additional support during tax season or wants the entire Self Assessment tax preparation team, we can work according to your requirements. Our support is tailored to your current workflow and, as agreed, we leave your practice in charge of all client communication, final review, approval and submission.
Service scope
Self Assessment work you can outsource
See the full scope at a glance, then explore the detail that matters to your practice.
01 / Client information
Client Information & Document Review
We review the information supplied by your team and organise it for efficient return preparation.
- Review client tax information
- Check previous-year returns
- Organise income and expense records
- Identify relevant return sections
- Flag missing information
- Highlight unclear or inconsistent items
02 / Return preparation
SA100 Tax Return Preparation
We prepare the Self Assessment tax return using the information your team provides and the work we agree on. Our self-assessment tax return outsourcing services may include:
- Prepare SA100 sections
- Enter relevant income information
- Review figures against records
- Include applicable supplementary pages
- Check internal consistency
- Prepare review-ready draft output
03 / Source review
Income & Expense Review
Support can cover multiple income types depending on the client and agreed engagement.
- Employment income
- Self-employment income and expenses
- UK property income
- Savings and dividends
- Pension income
- Foreign income and capital gains
04 / Calculations
Tax Calculations & Reconciliation
We prepare supporting calculations and reconcile relevant information for your team’s review.
- Income Tax calculations
- Review of tax deducted
- National Insurance calculations
- Capital Gains Tax calculations
- Payments on account
- Balancing payment / repayment review
05 / Reviewer support
Supporting Schedules & Review Notes
Clear working papers help your reviewers understand what has been prepared and what remains outstanding.
- Supporting tax calculations
- Income and expense summaries
- Reconciliation schedules
- Missing-information trackers
- Outstanding query lists
- Discrepancy notes
06 / Backlog support
Previous-Year & Outstanding Returns
Use project capacity for past-year or backlog preparation work where your practice needs additional resource.
- Defined backlog projects
- Previous-year return preparation
- Missing-document tracking
- Working paper preparation
- Query logs
- Review-ready drafts
07 / Practice support
HMRC Query Preparation Support
Where agreed, we can help prepare information and working papers your practice needs to respond to HMRC correspondence.
- Document collation
- Response working papers
- Information summaries
- Query tracking
- Supporting calculations
- Firm-controlled communication
08 / Ongoing capacity
Year-Round Tax Support
Beyond January, our team can support ongoing preparation, outstanding returns and workflow management.
- Recurring preparation capacity
- Previous-year returns
- Missing-information identification
- Supporting calculations
- Review-ready deliverables
- Flexible workload allocation
Need more Self Assessment capacity before peak season?
Add preparation resource without increasing permanent in-house headcount.
Our Expertise
Self Assessment & Accounting Support for UK Accounting Firms
Apart from Self Assessment tax return preparation services, we provide outsourced accounting services to help accounting firms and businesses manage their accounts, payroll, and tax reports.
Accounts Receivable
Accounts Receivable
Manage invoice processing, customer reconciliations and payment tracking with reliable back-office support.
Bookkeeping Services
Bookkeeping Services
Keep financial records up to date with transaction recording, bank reconciliations and ledger maintenance.
Tax Return Services
Tax Return Services
Get support with tax return preparation, tax calculations and supporting documents for your clients.
Payroll Services
Payroll Services
Simplify payroll processing with support for employee pay records, payroll calculations and reporting.
Year-End Accounts
Year-End Accounts
Prepare for year-end with reconciliation support, financial statements and organised working papers.
Corporation Tax Services
Corporation Tax Services
Get support with Corporation Tax computations, CT600 return preparation and supporting tax schedules.
VAT Services
VAT Services
Manage VAT records, transaction checks and VAT return preparation to support accurate reporting.
Client situations
Self Assessment Tax Returns for Your Clients
Our outsourced preparation services cater to those UK accounting firms that deal with clients with varied income sources and tax reporting needs.
Landlords & Property Owners
Prepare tax returns for clients with UK rental income, plus relevant adjustments and expenses.
Company Directors
Self Assessment preparation for directors with dividends, employment benefits (and other reportable income) that have caused their filing duties.
Freelancers & Contractors
Self-employment income and other relevant tax information for freelance or contractor work.
Investors & Individuals with Multiple Income Sources
Dividend and savings income, capital gains and other taxable income support for clients.
Persons having Foreign Income
Preparation of relevant Self Assessment data for UK taxpayers who are required to report overseas income.
Common Self Assessment forms
Self Assessment Tax Returns for Personal Taxation
Main Form: SA100: Personal Self Assessment Tax Return
| Form | Purpose |
|---|---|
| SA100 | Main Individual Self Assessment Tax Return |
| SA102 | Employment Income |
| SA103S/SA103F | Self-employment income: short and full versions |
| SA105 | UK Property Income |
| SA106 | Foreign Income |
Why Aone
Why Choose Us for Your Self Assessment Tax Return?
01
White-Label Support for Accounting Firms
We work as part of your accounting practice, with your workflow determining when we prepare and submit draft Self Assessment returns, while you retain control over clients and the submission of their returns.
02
Flexible Tax-Season Capacity
Increase your tax return preparation capacity during busy periods without having to recruit additional permanent employees. Our team works with your accounting practice, based on agreed workload and deadlines.
03
Review-Ready Tax Returns
We provide draft returns, supporting calculations, and working papers with outstanding queries to help your team complete returns in a timely, efficient manner.
04
Experienced Outsourcing Partner
Since 2011, Aone Outsourcing has been offering outsourced accounting and Self Assessment tax return services. We know the value of efficient processes, effective communication and reliable support in the back office for accounting procedures.
05
Confidentiality & Data Security
We know how important personal tax and financial data is. We adhere to agreed confidentiality, access and sharing of documents in order to maintain the confidentiality of the client.
06
Flexible Engagement Models
From support for selected Self Assessment returns, seasonal workloads or a dedicated team in your practice, we can discuss an engagement model that is suitable for your needs.
Our Process
How Our Process Works
Understand Your Clients' Requirements
We understand your clients' requirements, the self-assessment tax return volume you have and the seasonal capacity you demand. We also understand your existing review process and work according to your accounting workflow.
HMRC & MTD awareness
HMRC Self Assessment Compliance & MTD Awareness
UK accounting firms and practices must be aware of applicable HMRC requirements. It is very important to stay compliant with UK regulations; our team can help you with:
- We help you with timely submissions to HMRC and Companies House.
- We provide complete support for Making Tax Digital.
- We are certified and aligned with UK GAAP and ISO 9001 and ISO 21001.
Making Tax Digital for Income Tax
Making Tax Digital is now mandatory for UK income tax payers to keep their records digital, submit quarterly updates, and file annual declarations. Here are the key thresholds and important updates:
Over £50,000Mandatory starting 6 April 2026 (2024–2025 records)
Over £30,000Mandatory starting 6 April 2027 ( 2025–2026 records)
Over £20,000Mandatory starting 6 April 2028 (planned threshold)
Engagement models
How Much Does Self Assessment Tax Return Outsourcing Cost?
Dedicated Tax Preparation Expert
Hire a dedicated tax expert to manage your SA100 return preparation and supporting documents.
Build Your Tax Preparation Team
Build a team of tax experts to manage your high-volume Self Assessment tax return operations for your firm.
Project-Based Support
Get support for specific batch or past-year self-assessment preparation tasks or choose us for seasonal workloads.
Part-Time Tax Preparation Support
Get flexible support for SA100 preparation tasks for lower-volume tasks or for short durations.
★ Integrations
Software We Work With
We understand that UK accounting firms and practices have different tax requirements and we work with most UK tax firms.
In Our Clients' Words
What Our Clients Say
Aone gets it right and submits accurate, fully compliant self-assessment tax returns that fit perfectly with our UK clients' filing requirements.
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Frequently Asked Questions
Find answers to common questions about our outsourcing services
A Self Assessment tax return is an annual tax report used by HM Revenue and Customs (HMRC) in the UK. Self assessment tax return is the remaining tax liability that an individual calculates and pays individually when the tax has already been paid through sources like Tax Deducted at Source (TDS), Tax Collected at Source (TCS) and other advance tax. Accountancy firms and accountants can leverage the benefits of self-assessment tax return outsourcing to manage workload and increase in-house capacity.
You don't need to file a Self Assessment tax return if your income is already taxed through PAYE (Pay As You Earn). But it is important to file your self assessment tax return uk as you are self-employed and getting income from different sources such as savings, investments, or other untaxed income. If you're unsure, check the information on Who must send a tax return on HMRC.
The UK tax year usually runs from 6 April to 5 April of the following year. The deadline for the online tax return falls on 31st January following the end of the tax year. For offline paper submission, the deadline is 31 October.
The Personal Allowance is the amount of income you can earn each tax year without paying tax. According to the latest information, the standard Personal Allowance is £12,570. This amount can change, so it's important to check the current rates on the official HMRC website. The personal allowance is the amount of income you can earn each year without paying tax.
Here is the list of people who need to file a Self Assessment tax return:
- Self-Employed Individuals: Sole traders meeting HMRC's filing requirements.
- Landlords: Individuals who have rental income that must be reported.
- Company Directors: Directors who have income or tax obligations and need Self Assessment.
- Freelancers and Contractors: Individuals who have taxable income outside PAYE that must be reported.
- Investors: Individuals who have reportable capital gains, dividends, or other taxable investment income.
- Individuals With Foreign Income: UK taxpayers who have overseas income that requires reporting.
Scale tax preparation capacity
Tackling Staff Shortage and In-house Capacity in the UK?
Are you struggling with staff shortages and want to increase in-house capacity without expanding your accounting team in the UK? Don't wait; you can request a no-obligation 15-day free trial with us.