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Self Assessment tax returns

Your UK tax return, done for you, accurate, on time, no stress.

If you're a contractor, agency or umbrella worker, self-employed, a landlord or a director, you may have to file a Self Assessment. We handle the whole return, and make sure you claim everything you're allowed.

31 January deadline in hand Claim every allowable expense Secure & confidential
✓ UK-based tax specialists
✓ Fixed, transparent fees
✓ We chase you so you don't miss deadlines
✓ Secure data handling
✓ Professional indemnity insured
✓ ICO registered
✓ Named, personal support
Who it's for

If you earn outside a normal payslip, this is for you

Many people with income that isn't taxed at source have to file. We make it painless.

VERY COMMON

Contractors, agency & umbrella workers

Expenses to claim, multiple assignments, or income your umbrella didn't fully tax, we sort the return.

Self-employed & CIS subcontractors

Sole traders and CIS workers, we calculate your profit, claim your costs and reclaim CIS deductions.

Landlords

Rental income, mortgage interest relief and allowable costs, handled correctly and on time.

Directors & higher earners

Dividends, multiple income sources, or income over £100k, we keep it accurate and compliant.

The Self Assessment headache

Tax returns are stressful when you go it alone.

  • ✗ Miss the 31 January deadline and HMRC fines start at £100, and grow.
  • ✗ It's easy to over-pay by missing allowable expenses and reliefs you're entitled to.
  • ✗ The form is confusing, and a mistake can mean penalties or an enquiry.
  • ✗ Making Tax Digital for Income Tax started in April 2026 for sole traders and landlords with qualifying income over £50,000, and widens to over £30,000 in April 2027 and over £20,000 in April 2028.

How Onshore fixes it

Send us your details once; we do the rest and tell you exactly what to pay and when.

  • ✓ We prepare and file your full return, checked by a person before it's submitted.
  • ✓ We claim every allowable expense and relief so you don't over-pay.
  • ✓ We track your deadlines and chase you in good time, no last-minute panic.
  • ✓ Fixed fee agreed up front. Plain English. No jargon.
What's included

Everything your return needs

Full SA100 return

We prepare and file your complete Self Assessment return with HMRC on your behalf.

All income sources

Employment, self-employment, rental, dividends, interest, CIS, captured and reported correctly.

Expenses & reliefs

We claim the allowable expenses and reliefs you're entitled to, so you pay the right amount, not more.

Deadlines & HMRC

We manage the dates, deal with HMRC, and tell you exactly what to pay and when.

Free 30-second check

Do you need to file a Self Assessment?

Answer a few quick questions for an instant indication. No email required.

1. In the last tax year, did you earn more than £1,000 (before expenses) as a self-employed sole trader, freelancer or CIS subcontractor, or were you a business partner?
How it works

Three simple steps

1

Send us your info

A short, secure checklist of your income and expenses, we tell you exactly what we need.

2

We prepare & check

We build your return, claim your allowances, and a person reviews it before anything is filed.

3

We file & you relax

We submit to HMRC and tell you exactly what to pay and when. No deadline panic.

Pricing

Fixed fees, you'll always know the price up front

Indicative starting prices. Your exact fixed fee is agreed before we start.

Simple

Employment + one extra income source (e.g. small dividends)
from £145one-off
  • ✓ Full SA100 prepared & filed
  • ✓ One income source beyond PAYE
  • ✓ Deadline managed for you
Get a quote

Self-employed / Landlord

Sole traders, contractors, CIS, rental income
from £200one-off
  • ✓ Everything in Simple
  • ✓ Self-employment or rental accounts
  • ✓ Expenses & reliefs claimed
  • ✓ CIS deductions reclaimed
Get a quote

Complex

Multiple income sources, higher earners, directors
from £375one-off
  • ✓ Multiple income streams
  • ✓ Income over £100k / directors
  • ✓ Capital gains, foreign income, etc.
  • ✓ Priority support
Talk to us

Registering you for Self Assessment, if you are not registered yet, is £35, and free if you are already a payroll client of ours. Limited company director? The Director Bundle covers your payroll and your return from the tax year it starts, from £85/mo, with a 12-month minimum term. Company accounts and Corporation Tax are not included. No VAT is added to our fees, the price you see is the total, while many firms add 20% on top. Final fixed fee depends on complexity and is confirmed before we start. CIS subcontractors: we'll check whether you're owed a refund. If an online return reaches HMRC after 11:59pm on 31 January, HMRC charge a late filing penalty, which is paid to HMRC, not to us. Ask about a small annual retainer if you file every year.

Key dates

The Self Assessment calendar

5 October

Register for Self Assessment if it's your first return, or if you're registered but didn't need to file for the previous year (after the tax year ends).

31 October

Deadline for paper tax returns.

31 January

Online return deadline and your tax payment (plus first payment on account).

31 July

Second payment on account, if applicable.

Get started

Get your fixed-fee quote

Tell us a little about your situation and we'll send a fixed-fee quote within one UK business day.

Indicative fixed fee from
£...
one-off, confirmed before we start
Email us for my exact quote
FAQ

Self Assessment questions, answered

How do I know if I need to file?

You usually need to file if you were self-employed (including as a CIS subcontractor) and earned more than £1,000 before expenses, were a business partner, had Capital Gains Tax to pay, or had to pay the High Income Child Benefit Charge and don't pay it through PAYE. Other income can mean a return too: rental profit over £2,500 (or rent over £10,000), savings interest or dividends over £10,000, or £2,500 or more of other untaxed income. Smaller amounts are usually reported to HMRC without a return. Use the free checker above, or just ask us, we'll confirm.

What do you need from me?

A simple, secure checklist: your income (P60/P45, self-employment or rental figures, dividends, etc.) and any expenses. We tell you exactly what to send and chase anything missing.

What does it cost?

A fixed fee agreed up front, from £145 for a simple return, from £200 for self-employed/landlord, from £375 for complex. Registering you for Self Assessment, if you are not registered yet, is £35, and free if you are already a payroll client of ours. No surprises.

Can you stop me missing the deadline?

Yes, that's part of the service. We track your deadlines and chase you in good time so you avoid the £100+ late-filing penalties.

What about Making Tax Digital?

MTD for Income Tax started in April 2026 for sole traders and landlords with qualifying income over £50k, and widens to over £30k in April 2027 and over £20k in April 2028, each based on your qualifying income two tax years earlier. It means digital records and quarterly updates, and you still file a tax return after the year ends. If it affects you, we'll set you up the right way.

Is my data safe?

Yes. We collect documents through a secure channel, never insecure email, and handle your information confidentially and in line with UK GDPR.

Free tool

Work out your take-home pay

Weighing up salary, dividends or a contract rate? Our free calculators show your take-home pay, gross up a target salary, and the true cost of a hire, for 2025/26 and 2026/27.

Try the free calculators →

Leave your tax return to us

Get a fixed-fee quote today, accurate, on time, and no jargon.

Get a quote
✓ Ask us on WhatsApp✓ Fixed fees, published✓ No lock-in on payroll✓ £250 off setup on a DPNI, a DCNI, an NI-only or a tax-only scheme, if you go ahead quickly