Your tax return, sorted.Without the headache.
Send us your information and we'll take it from there. An Addition accountant prepares your return, you approve it in the Addition app, and we'll submit it to HMRC.
Your 2025/26 return
Review your tax position and approve securely.
Tax returns don't need to be complicated.
No spreadsheets flying backwards and forwards. No confusing HMRC forms. No wondering what happens next.
Everything you need to complete your Self Assessment in one app.
Self Assessment in four simple steps.
Tell us about yourself
Answer a few simple questions so we understand your income and tax situation.
Upload your documents
Upload everything we need securely through the Addition platform.
We prepare your return
An Addition accountant reviews your information and prepares your Self Assessment.
Review. Approve. Done.
We'll send your completed return approval. Once you're happy, approve it and we'll submit it to HMRC.
Tell us about yourself
Which sources of income did you have?
Upload your documents
Your return is being prepared
We'll notify you as soon as it is ready to review.
Your return is complete
Estimated tax due
£2,840.00Everything needed for your UK Self Assessment return.
Everything in one place.
Forget email chains, attachments and chasing your accountant for updates. Your entire Self Assessment lives inside Addition.
Upload documents
Send us what we need securely from your phone or computer.
Track progress
See exactly where your return is in the process.
Review your return
See your completed return and tax position before anything is submitted.
Approve from anywhere
Approve your return through Addition and we'll take care of submission.
Everything is on track
Need to file a Self Assessment?
Not sure if your return is covered? We'll check your situation when you get started. More complex tax affairs may require additional support, which we'll discuss with you before proceeding.
From start to finish.
Your journey, step by step.
You can follow your return from start to finish inside Addition.
A simpler way to do your Self Assessment.
One less thing on your to-do list.
Let Addition take care of your Self Assessment.
Prepared by an accountant. Approved by you. Filed with HMRC.
Frequently asked questions
Do you actually submit my tax return?+
Yes. Once your return has been prepared, you'll review and approve it through Addition. We then submit it to HMRC for you.
What information will I need?+
This depends on your circumstances. Once you get started, we'll tell you exactly what information and documents we need.
Do I need a UTR?+
If you're required to file a Self Assessment, you'll normally need a Unique Taxpayer Reference. If you're filing for the first time and don't have one yet, we'll explain the relevant registration process.
How long does it take?+
Timing depends on receiving all the required information and documents from you. Once we have everything, your accountant prepares your return and you'll be notified to review and approve it.
Can I track my return?+
Yes. You'll be able to see your return's progress through Addition at every stage.
Will I see my tax bill before you submit?+
Yes. Your completed return will be made available for you to review and approve before submission.
What if my tax affairs are complicated?+
The £119 service is intended for returns that fall within the standard service scope. If additional work is required, we'll let you know before proceeding.
Is £119 the full price?+
Yes, for a standard Self Assessment covered by the service. It's a one-off payment, not a subscription.
Can I ask questions?+
Yes. Customers can contact the Addition team during the preparation of their return.
