Running More Than One Business

Introduction

If you're running more than one self-employed business, you have choices about how to report them on your Self Assessment tax return. While you must keep separate records for each business, you can often combine them on your return — though there are important situations where you must keep them separate, particularly when it comes to losses and National Insurance contributions.

Keeping Records for Each Business

You must maintain separate accounting records for each business you run. This means keeping distinct records of income and expenses for each trade or profession, even if you plan to combine them on your tax return.

Keeping separate records helps you:

• Track which businesses are profitable and which are making losses
• Make informed decisions about each venture
• Correctly apply tax rules that depend on individual business performance
• Provide HMRC with accurate information if they enquire about a specific business

Combining or Separating Businesses on Your Tax Return

When completing your Self Assessment tax return, you can usually combine all your self-employed businesses into a single entry on one self-employment page. This simplifies your return and means you only need to complete one set of boxes for your total business income and expenses.

However, you must report businesses separately if:

• Any business made a loss that you want to claim relief for
• Your businesses have different accounting dates (the date to which you make up your accounts each year)
• You want to keep the businesses separate for any other reason

Dealing with Business Losses

If one or more of your businesses makes a loss, you cannot combine that business with your profitable ones on the same self-employment page. Each loss-making business must be shown separately on its own page of the tax return.

This separation is necessary because:

• Loss relief rules apply to each trade individually
• You need to show HMRC exactly which business made the loss
• Different loss relief claims have different conditions and you must demonstrate you meet them

Your profitable businesses can still be combined together on a single page, as long as they share the same accounting date.

National Insurance Implications

Running multiple businesses affects your National Insurance contributions, specifically Class 4 contributions which self-employed people pay on their profits.

Class 4 National Insurance Contributions

Class 4 National Insurance is calculated on your total profits from all self-employed businesses combined. For the 2025/26 tax year, you pay Class 4 at the following rates:

• 6% on profits between £12,570 and £50,270
• 2% on profits above £50,270

When you have multiple businesses, HMRC adds together all your self-employment profits to work out your Class 4 liability. This happens automatically when you complete your tax return — you don't calculate Class 4 contributions separately for each business.

Class 2 National Insurance Contributions

You should also be aware that if your total profits from all businesses combined exceed the Small Profits Threshold, you must pay Class 2 National Insurance contributions. These are collected through Self Assessment alongside your other tax.

Partnerships and Multiple Businesses

If you're a partner in one or more partnerships as well as running sole trader businesses, different rules apply:

• Each partnership must always be shown separately on your tax return (on the partnership pages)
• Your sole trader businesses follow the rules above — they can be combined unless one makes a loss or has a different accounting date
• You cannot combine partnership income with sole trader business income

Accounting Dates

Your accounting date is the date to which you prepare your accounts each year — often 31 March or 5 April, but it can be any date you choose.

If your businesses have different accounting dates, you must report them on separate pages of your tax return. You cannot combine businesses with different accounting periods because:

• Each business's taxable profits relate to a different 12-month period
• The basis period rules (how HMRC matches your accounts to tax years) may differ
• It would be impossible to correctly calculate your tax liability

Where possible, aligning your accounting dates across all businesses simplifies your tax return and reduces administrative burden.

Interest and How It's Allocated

If you have business bank accounts that earn interest, and you're combining multiple businesses on one tax return page, you should add together the interest from all accounts relating to those businesses. The total interest is shown in the relevant box on the self-employment page.

If you're keeping businesses separate (for example, because one made a loss), report the interest on the page relating to the business whose bank account earned it.

Practical Tips

When running multiple businesses:

• Use separate bank accounts for each business to make record-keeping cleaner
• Choose the same accounting date for all your businesses where practical
• Review each business separately at year-end to identify losses before completing your tax return
• Consider whether combining businesses on your return makes sense, or whether separate reporting provides better clarity
• Keep clear records showing which income and expenses relate to which business, even if you combine them on your return

Remember that choosing to combine businesses on your tax return is about presentation to HMRC — it doesn't change your underlying obligation to maintain separate accounting records for each trade.

Sources

• More than one business (Self Assessment helpsheet HS220)

This article provides general guidance based on current HMRC rules. For advice specific to your situation, speak to your accountant.