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Self Assessment software for bookkeepers

You already keep the books for sole traders and landlords. Turn the year’s figures into their Self Assessment return, prepared free and filed under your agent login for one credit each.

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SA103 short and full
UK property
Agent filing
Pay per filing

selfassessmentsoftware.co.uk/clients/…/sa103

← Return 2025-26

Self-employment · 1st

SA103S 2026 · one page set per business.

Business income - if annual turnover was below £90,000

9Your turnover - takings, fees, sales or money earned£58,400.00

10Any other business income not included in box 9£0.00

Allowable business expenses

11Costs of goods bought for resale or goods used£6,120.00

12Car, van and travel expenses - after private use£3,480.00

14Rent, rates, power and insurance costs£2,150.00

18Phone, fax, stationery and other office costs£640.00

20Total allowable expenses - total of boxes 11 to 19£12,390.00

Net profitSA103S

Turnover £58,400 less expenses £12,390 gives a profit of £46,010.

£0to prepare every client’s return

1 creditper client tax year when you file

£90,000turnover line between SA103S and SA103F

Unlimitedlogins for seasonal help

In short

A bookkeeper can prepare and file clients’ Self Assessment returns with a practice account: add the client, enter the year’s totals on the self-employment and property pages, and file with your HMRC agent login once the client approves. Preparing is free and each filing uses one credit. You need HMRC agent credentials, which means anti-money laundering supervision, and each client’s authorisation.

This page covers

Turning year-end books into SA103 and SA105
Agent filing and client approval
Where professional judgement is needed

Not covered here

Workflow

From the ledger to the return

The figures are already reconciled in your bookkeeping software. The return is a short final step.

01 Step 1 of 4

Close the books, then open the return

Run profit and loss for the accounting period that ends in the tax year. Add the client once with their NINO, UTR and address, then start the 2025-26 return and tick the pages they need.

One page set per business: a client with two trades gets two self-employment pages. Property lets and a PAYE job are ticked alongside.

In the appClients → Add client → Start a return

Good to know

Check the accounting date. Since basis period reform, profits are taxed for the tax year, not the accounting year.

02 Step 2 of 4

Short page under £90,000 turnover

Most sole traders you look after can use SA103S. Enter turnover in box 9 and either itemise expenses in boxes 11 to 19 or put one total in box 20.

Itemising takes a few extra minutes from a trial balance and gives the client a clearer calculation.

In the appSelf-employment · SA103S

← Return 2025-26

Self-employment · 1st

SA103S 2026 · one page set per business.

Business income - if annual turnover was below £90,000

9Your turnover - takings, fees, sales or money earned£58,400.00

10Any other business income not included in box 9£0.00

Allowable business expenses

11Costs of goods bought for resale or goods used£6,120.00

12Car, van and travel expenses - after private use£3,480.00

14Rent, rates, power and insurance costs£2,150.00

18Phone, fax, stationery and other office costs£640.00

20Total allowable expenses - total of boxes 11 to 19£12,390.00

03 Step 3 of 4

Full page when the business is bigger

Turnover of £90,000 or more, CIS subcontractors or more adjustments mean SA103F. Expenses run from box 17 to box 30, with a separate section for disallowable amounts included in those figures.

Box 31 totals the expenses as you type, so you can reconcile straight back to the profit and loss.

In the appSelf-employment · SA103F

Good to know

Depreciation goes in box 29 and is added back in the disallowable section; claim capital allowances instead.

← Return 2025-26

Self-employment · 1st

SA103F 2026 · one page set per business.

1 Details2 Expenses3 Profit4 Taxable profit

Allowable expenses

17Cost of goods bought for resale or goods used£41,300.00

18Construction industry - payments to subcontractors£18,750.00

19Wages, salaries and other staff costs£22,400.00

20Car, van and travel expenses£5,910.00

24Advertising and business entertainment costs£1,200.00

Box 31 is the total of boxes 17 to 30. It updates as you enter expenses.

04 Step 4 of 4

Show the client the bill before you file

Reports gives you the SA302-style calculation, a tax letter, a payment note and a detailed schedule. Email the payment note so the client sees January and July amounts before they approve.

Then send the approval email from the filing desk. You file with your agent login once the client approves.

In the appReports → Tax payment → Email to client

← Return 2025-26

Reports · 2025-26

SA302 computation, tax letter, payment note and detailed schedule for Dan Hughes.

SA302 ComputationTax letterTax paymentDetailed schedule

Payment note emailed to the client.

Tax payment note

What to pay HMRC · 2025-26

What	Due	Amount
Balancing payment for 2025-26	31 January 2027	£3,104.00
First payment on account for 2026-27	31 January 2027	£4,347.00
Second payment on account for 2026-27	31 July 2027	£4,347.00

Reconcile

Which report feeds which box

Where each year-end figure from the books lands, so the return ties back to your working papers.

From your books	SA103S	SA103F	Tie back to
Sales and fee income	Box 9	Box 15	Profit and loss turnover
Grants, rebates, other income	Box 10	Box 16	Other income lines
Total expenses, one line	Box 20	Box 30	Profit and loss total costs
Itemised expenses	Boxes 11 to 19	Boxes 17 to 30	Nominal ledger by heading
Subcontractor payments (CIS)	See HMRC’s SA103S notes	Box 18	CIS300 returns for the year
Disallowable items in the totals	Exclude before entry	Boxes 32 to 45	Journal of add-backs
Equipment and vans bought	Capital allowances	Capital allowances	Fixed asset register

Box numbers are from the 2025-26 pages in the desk. Always check HMRC’s notes for the year you file.

Judgement calls

When to bring in a tax adviser

The desk has every page, but some years need judgement as well as data entry. Agree a referral partner before the season starts.

Disposals with reliefs

Selling a business, a let property or shares where reliefs or the 60-day property return apply.

Residence questions

Clients arriving in or leaving the UK, split years and overseas workdays.

Foreign income

Overseas rental or employment income with foreign tax credit relief.

Trusts and estates

Income from a trust or a deceased person’s estate.

HMRC enquiries

Compliance checks, disputes and appeals.

Incorporation

Whether a growing sole trader should become a limited company.

Before your first filing

What you need to file for clients

HMRC does not require an accountancy qualification to act as an agent, but it does require supervision and authorisation.

Anti-money laundering supervisionHMRC asks for your supervisor when you register as an agent. Many bookkeepers are supervised through their professional body.

An agent services accountYour agent Government Gateway user ID is what the desk files with.

Each client’s authorisationRequest it through HMRC before the first filing for that client.

Engagement lettersAgree in writing that you prepare from records the client provides, and who approves the return.

Agent authorisation guide Save your agent login →

Pricing

No subscription, pay per filing

Prepare as many returns as you like. Each filing uses one credit for that client’s tax year, including any resubmission or amendment for the same year.

10 credits

£99 + VAT

£9.90 per filing

Most chosen

25 credits

£199 + VAT

£7.96 per filing

50 credits

£349 + VAT

£6.98 per filing

100 credits

£549 + VAT

£5.49 per filing

250 credits

£999 + VAT

£4.00 per filing

Compare credit packs →

FAQs

Common questions

Can a bookkeeper file Self Assessment returns for clients?

Yes, once HMRC has authorised you as the client’s agent. HMRC does not require an accountancy qualification, but you must be supervised for anti-money laundering.

Can I import figures from Xero or QuickBooks?

Not directly. Enter the year totals from your bookkeeping reports. The pages follow HMRC’s headings, so a profit and loss maps across in minutes.

What does it cost a bookkeeper?

Preparing returns is free. Each filing uses one credit for that client’s tax year, bought in packs.

Do I need a practice account or an individual account?

A practice account. Individual accounts are for filing your own return only.

Does it send MTD quarterly updates?

No. It prepares and files the annual Self Assessment return. MTD quarterly updates are not offered yet.

Keep going

Prepare free

Turn this year’s books into this year’s returns.

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