Self Assessment Tax Return UK Outsourcing for Accounting Practices
Self assessment tax return UK preparation, handled as an extension of your own tax team. SA100 compliant returns delivered in 5 working days, reviewer ready, senior tax reviewed, and packaged for clean client sign off.
Built for UK Accounting Practices of Every Size.
Whether you're managing a January backlog, covering a staff gap, or scaling through peak season, our self assessment tax return UK team slots directly into your existing workflow without disruption.
Solo & Small Practices
- Affordable per return pricing, no retainer
- No minimum volume commitment
- Same 5 day turnaround from day one
- Works in your existing software
Growing Firms
- Scale instantly at peak (Jan 31st & July 31st)
- No permanent headcount required
- Dedicated account contact for your firm
- Senior tax reviewed output every return
Mid Size & Multi Office Groups
- High volume capacity on demand
- Consistent return standards across offices
- Monthly volume reporting & SLA tracking
- Complex cases: CGT, foreign income, trusts
Everything Covered,
SA100 to Submission.
From source documents to reviewer ready returns. Our self assessment tax return services cover every stage of preparation so your team focuses on client relationships and sign off.
SA100 Self Assessment Tax Return Preparation
- SA100 core return with all required supplementary pages
- SA103 (sole trader) & SA105 (property income)
- SA106 (foreign income) & SA108 (capital gains)
- SA102 employment income schedules
Source Document Organisation
- Structured handling of client-supplied records
- Income and expense categorisation schedules
- Rental income reconciliations and schedules
- Investment and dividend income schedules
Tax Computations
- Multi-source income calculations
- Capital gains tax computations
- Pension contribution relief calculations
- Gift Aid carry back claims
Reviewer Ready Delivery
- Open point query logs for the reviewer
- Reviewer handover notes with sign-off checklist
- Version controlled file delivery
- Revisions and amendments included
Your clients' software.
Our team knows it.
No onboarding friction. No tool switching. Our self assessment tax return UK team steps straight into the software your practice already runs on and gets to work from day one.
Talk to our team
Don't see your software? We adapt to your needs. — including MTD compatible packages as your UK self assessment client base moves onto quarterly reporting.
Self Assessment Outsourcing: But Why?
Because your senior team's time is worth more than return preparation. Here's exactly what self assessment tax return outsourcing gives you back.
Focus on Client Relationships
Free your senior team from return preparation. Spend that time on tax planning, client conversations, and growing your advisory practice.
Save Up to 50% in Costs
Eliminate the overhead of a full time tax technician. Pay only for the returns you need, with no salaries, NI, or desk space during quiet months.
Expert Tax Team on Every Return
Every return is checked by a self assessment accountant UK practices would be happy to put in front of a client. You receive reviewer ready output, not a draft that needs significant rework.
No Software Migration
We work directly inside IRIS, TaxCalc, CCH, or Capium from day one. Your workflow, your templates, your review process, unchanged.
Flexible Peak Capacity
Instantly add self assessment resource during the January 31st and July 31st deadlines. Scale back when the pressure eases. No permanent commitment.
Six Reasons UK Firms Choose Us for Self Assessment Tax Return Outsourcing.
Expert reviewed output, guaranteed turnaround, and seamless software compatibility, the self assessment tax return services UK practices stay with, from a partner built specifically for UK accounting firms.
Up to 50% cost saving
Reduce return preparation cost compared to equivalent UK senior staff, without sacrificing quality or review oversight.
5 day turnaround
Consistent delivery in 5 working days from receipt of source documents, even during January and July peak periods.
HMRC compliant returns
Our HMRC self assessment services cover SA100 with all required supplementary pages, accurate computations, structured query logs, and MTD quarterly updates where your clients are in scope.
Senior tax reviewed output
Every return is quality checked by a qualified tax professional before delivery, and you receive reviewer ready work.
Scalable peak capacity
Add self assessment resource instantly during January and July deadline periods. No permanent headcount and no minimum volume.
GDPR secure delivery
NDA signed before work begins. Encrypted file transfer, role based access controls, and full GDPR compliance throughout.
How Our Self Assessment Tax Return UK Service Works
Share Source Documents
Secure file upload via our portal
Return Preparation
Prepared by qualified tax professionals
Senior Tax Review
Reviewed by an experienced senior tax professional
Quality Check
Multi-level quality assurance
Client Ready Delivery
Delivered in 5 working days, ready for client sign off
Built for the MTD Era, Not Last Season's Rules
Making Tax Digital for Income Tax went live on 6 April 2026, and more than 864,000 sole traders and landlords with qualifying income over £50,000 are now inside it. The first quarterly update fell due on 7 August 2026, with the rest following on 7 November, 7 February and 7 May. The threshold drops to £30,000 in April 2027 and £20,000 in April 2028, so the population your practice files for grows every year.
Quarterly updates do not replace the return. Clients still file by 31 January, and all four updates must be submitted before the return can go in. From April 2027 the points-based penalty regime extends to every self assessment taxpayer, not only those inside MTD.
Our self assessment tax return UK specialists work to the current year's rules as standard, and we are already running quarterly update cycles alongside the 2025/26 returns due on 31 January 2027.
"Probal Global transformed our self assessment season. We went from working weekends in December and January to delivering every return on time with capacity to spare. The returns arrive clean, the query logs are thorough, and our team can actually focus on the clients rather than staring at spreadsheets."
£35k+
Annual saving in staffing costs
Probal Global vs. Your Other Options.
See why UK practices choose dedicated self assessment tax return outsourcing over in house preparation or ad hoc freelancers.
Real questions from UK accountancy practices answered honestly.
If you're considering self assessment tax return UK support for the first time, you probably have a few questions. Here are the ones we get asked most, with straight answers.
Still have questions? Get in touchYes. We work directly inside your existing tax software so there is no migration and no change to your internal review workflow. We adapt to your templates and file structures from day one.
We support all SA supplementary pages including SA102 (employment), SA103 (self-employment), SA105 (property), SA106 (foreign income), SA108 (capital gains), and SA109 (residence). We handle mixed income profiles and complex cases.
Capacity scales instantly. Most firms add dedicated self assessment resource from us in November through January. Work is allocated the same day it arrives and turnaround is maintained at 5 working days throughout peak.
We sign an NDA and DPA before any work begins. All files are transferred via encrypted channels. No client data is stored after delivery. We are GDPR registered and ISO 27001 aligned.
Yes. We log gaps early and return structured query logs so your client-facing team can resolve issues before deadlines tighten. This reduces review friction and last-minute chasing.
Revisions based on reviewer feedback are included at no extra charge. We aim to turn around revision files within 24 hours.
Pricing is per return, based on complexity rather than a flat headline rate. A straightforward employment and dividend return sits at one end; a return with multiple properties, foreign income and a capital gains computation sits at the other. There is no retainer, no minimum volume, and no separate charge for the senior review. Send us a sample of your client list and we will price it properly rather than quote a number that changes at return three.
All of the standard supplementary pages, plus the cases most firms find slowest: multiple property portfolios, foreign income with double taxation relief, capital gains including 60-day residential property reporting, partnership returns on SA800, CIS subcontractor returns with deductions to reclaim, High Income Child Benefit Charge, and payments on account reduction claims. If a case sits outside that, we will tell you before we take it rather than after.
Yes, and we are already working in it. MTD for Income Tax went live on 6 April 2026 for sole traders and landlords with qualifying income over £50,000, with the threshold dropping to £30,000 in April 2027 and £20,000 in April 2028. We handle the quarterly update cycle on 7 August, 7 November, 7 February and 7 May alongside the annual return. Quarterly updates do not replace the return — your clients still file by 31 January, and all four updates must be in before that return can be submitted.
Free Trial Available
Try Probal Self Assessment Free.
No Cost, No Commitment.
Send us a real client file. We'll prepare the return in your software, return a reviewer ready file in 5 days, and let the quality speak for itself. It is the lowest-risk way to test self assessment tax return outsourcing before you commit a single client to it.