Income Tax Losses in the UK: A Practical Guide for Small Businesses

This guide explains what income tax losses are, how the main reliefs work, and how to claim them through Self Assessment – with worked examples and planning tips geared towards UK small businesses.

What is an income tax loss?

An income tax loss arises when the deductible expenses, allowances, and reliefs attached to a source of income exceed the taxable income from that source in a tax year. In plain terms, you spent (or are allowed to deduct) more than you earned.

The concept goes by several names – "income tax losses," "tax losses," "trading losses" – but they all describe the same thing: a shortfall that HMRC lets you set against other income or carry to another year so that the money genuinely lost is not also taxed elsewhere.

How a loss differs from an accounting loss or a capital loss

These three figures can be wildly different for the same person in the same year.

A sole trader whose accounts show a profit can still have a tax loss once capital allowances are added. Conversely, a large accounting loss may shrink after disallowable expenses are added back. The numbers are rarely identical, so always work from the tax-adjusted figure.

Who do the rules apply to?

Income tax loss rules cover sole traders, partners in a partnership or LLP, UK property landlords, and investors claiming share loss relief on qualifying subscribed shares. They do not apply to limited companies (which follow Corporation Tax loss rules) or, in practice, to most employees – because employment income seldom generates a deductible loss.

Types of income tax losses

UK law recognises several categories of loss, each with its own relief mechanisms. The three that matter most to small businesses are trading losses, property income losses, and share losses.

Trading losses (sole traders and partnerships)

A trading loss is the bread and butter of small-business loss relief. It arises when the allowable expenses and capital allowances of a self-employed trade exceed its income for the tax year.

Calculating the loss. Start with turnover, deduct allowable revenue expenses, then deduct capital allowances (such as the Annual Investment Allowance). Add back any disallowable items – entertaining, personal use proportions, depreciation. The result, if negative, is the trading loss for that year. If you use the cash basis, the calculation follows cash in and cash out instead of accruals, but the principle is the same.

Once you have a trading loss, several relief routes are open to you. Which one saves the most tax depends on your other income, your marginal rate, and your time horizon.

Sideways relief against general income (ITA 2007 s 64)

You can set the loss against your general income – employment income, rental profits, savings interest, dividends – of the same tax year, or the previous tax year, or both (same year first if you claim both). This is called "sideways" relief because the loss moves across income types rather than staying within the trade.

The relief is all-or-nothing for each year you claim: you cannot restrict it to preserve your personal allowance. That means a large loss claim can "waste" your £12,570 personal allowance if your remaining income falls below it. Sometimes carrying forward is the better choice for exactly this reason.

Early years relief – first four tax years of trade (s 72)

If the loss falls in any of the first four tax years of a new trade, you can carry it back against general income of the three years before the loss year, setting it against the earliest year first. This can generate a sizeable refund for someone who was previously employed on a good salary and has just started a business.

Carry forward against future profits (s 83)

Unused trading losses can be carried forward indefinitely and set against the first available profits of the same trade. There is no time limit and no cap, but the relief only offsets profits from the same trade – not general income. Carry forward also reduces Class 4 National Insurance on those future profits.

Terminal loss relief on cessation (s 89–s 94)

When a trade permanently ceases, a loss arising in the final twelve months can be carried back against trading profits of the three tax years before the final year, latest year first. This is a powerful relief for anyone winding down a business, because it can unlock refunds from years when the trade was profitable.

Using a trading loss for CGT relief (s 71)

If you have used all available income against which to set the loss (or the income is taxed at lower rates than your capital gains), you can elect to treat all or part of the trading loss as a capital loss. The capital loss then offsets chargeable gains of the same tax year. The election must be made within the normal claim window.

Key restrictions

Not every trading loss qualifies for every relief. The main constraints are:

• Commerciality test (s 66). Sideways relief is only available if the trade is conducted on a commercial basis with a reasonable expectation of profit. A hobby business will fail this test.
• Hobby farming rule (s 67–s 69). If a farming or market-gardening trade has made losses in each of the previous five years, sideways relief is automatically denied unless you can show a reasonable expectation of future profit.
• Non-active trader restriction (s 74A). Where the taxpayer does not spend a significant amount of time in the trade (broadly, 10 hours a week on average), sideways relief is capped at £25,000.
• Annual relief cap. Sideways and early years relief are subject to the higher of £50,000 or 25 % of adjusted total income (see below).
• Cash basis restriction (from April 2024). Losses computed under the cash basis cannot be relieved sideways – only carried forward. To preserve sideways relief, you must elect for accruals.
• No double counting. The same loss cannot be used for more than one relief.

⚠️ Attention: Cash basis is now the default from 6 April 2024. If you are a sole trader or partner and have not actively elected for accruals, HMRC will assume you are using the cash basis. This means any loss you make can only be carried forward – you lose access to sideways relief, early years relief, and terminal loss relief. If there is any chance you may want those reliefs, elect for accruals accounting on your Self Assessment return before filing.

Property income losses

Losses in a UK property business arise when allowable expenses – repairs, insurance, agent fees, rates – exceed rental income. However, the rules here are narrower than for trading losses.

The mortgage interest restriction. Since April 2020, finance costs (mortgage interest and incidental costs of obtaining finance) for residential lettings are no longer deducted from rental income. Instead, landlords receive a basic-rate (20 %) tax credit. This means finance costs cannot create or increase a property loss. Only non-finance expenses can do so.

Using property losses. A UK property loss can only be carried forward and set against future profits of the same UK property business. There is no sideways relief, no carry-back, and no option to use it against capital gains. The loss carries forward indefinitely until the property business produces a profit.

Joint owners. Where a property is jointly owned, income and expenses – and therefore losses – are split according to actual ownership shares (or 50 : 50 for married couples and civil partners unless a Form 17 election is made).

Non-resident landlords follow essentially the same loss rules, though they register under the Non-Resident Landlord Scheme and may need to file a Non-Resident Company return if operating through a corporate structure.

Furnished holiday lettings (FHLs) have historically enjoyed more generous loss treatment (including sideways relief against general income), but the government announced that FHL tax advantages will be withdrawn. For 2024/25 the existing rules still broadly apply, but landlords should watch the legislation closely for 2025/26 onwards.

Share loss relief (losses on qualifying subscribed shares)

If you subscribed for shares in a qualifying trading company and those shares are disposed of at a loss – or are deemed of negligible value – you can claim income tax relief rather than the usual capital gains loss treatment. This is particularly relevant for investors in Enterprise Investment Scheme (EIS) and Seed Enterprise Investment Scheme (SEIS) companies, although it extends to other qualifying unquoted trading companies too.

Conditions. The shares must have been subscribed for (not bought second-hand), the company must have been a qualifying trading company throughout the relevant period, and the company's gross assets must not have exceeded £15 million before the share issue and £16 million immediately after. The investor must be UK-resident.

How it works. The allowable loss (disposal proceeds minus subscription cost, reduced by any EIS/SEIS income tax relief already received) is set against general income of the tax year of disposal, or the previous year, in the same way as sideways trading loss relief. Claims are made on the Self Assessment return (SA108) or by separate written claim and must be made within the normal time limits. HMRC Helpsheet HS286 sets out the detail.

A negligible value claim allows you to treat shares as disposed of and reacquired at nil value without an actual sale – crystallising the loss at the point the claim is made (or an earlier specified date). This is useful when the company is insolvent or its shares are genuinely worthless but no buyer exists.

Partnership losses

Partnership losses are allocated to individual partners according to the partnership agreement (or equally if silent). Each partner then claims relief on their personal Self Assessment return using the same trading loss reliefs described above.

However, two additional restrictions bite for certain partners. Limited partners (in a limited partnership) and non-active LLP members can only relieve losses sideways up to the amount of their capital contribution at risk. And the non-active partner restriction mirrors the sole-trader rule: where a partner spends fewer than 10 hours a week on the trade, sideways relief is capped at £25,000 per year (subject also to the annual relief cap).

Foreign and ring-fenced trades

Losses from a trade carried on wholly abroad can only be set against foreign income (not UK income), subject to detailed rules on residence, the remittance basis, and double taxation agreements. Losses from ring-fenced trades – mainly oil and gas extraction – are confined to profits of the same ring-fence and cannot be used sideways against other income. These situations are uncommon for most small businesses but merit specialist advice where they arise.

How to use and claim income tax losses

Choosing the best relief route

The "best" relief depends on your tax profile. A few rules of thumb:

If you have other income taxed at 40 % or 45 %, sideways relief in the current year is usually the most valuable option – you get the refund now at the highest marginal rate. If your other income is low or nil, carrying forward to set against future trade profits (taxed at your future marginal rate) may preserve more value. The CGT election is worthwhile only when you have gains that would otherwise be taxed and your income is already covered.

For new businesses, early years relief can be exceptionally powerful – carrying a Year 1 loss back to a year when you were employed full-time and paying 40 % tax.

For cessation, terminal loss relief is almost always worth claiming because it goes back three years against trading profits, effectively recovering tax already paid.

Time limits and deadlines

Missing a deadline means losing the relief permanently, so these dates matter.

For a 2024/25 loss, the filing deadline is 31 January 2026 and the claim deadline for sideways or early years relief is 31 January 2027.

How to claim via Self Assessment

Most loss relief claims are made through the Self Assessment tax return:

• SA103 (self-employment pages) – report the loss and tick the relevant relief boxes.
• SA105 (property pages) – report the property loss; carry-forward is automatic once declared.
• SA108 (capital gains pages) – use for share loss relief and the CGT election.
• SA100 (main return) – white-space notes can explain complex claims, attach computations if needed.

If you are not within Self Assessment (for example, you ceased trading and are no longer required to file), you can make a stand-alone claim by writing to HMRC within the normal time limit, enclosing the loss computation and any supporting evidence.

Evidence and recordkeeping

HMRC can enquire into any loss claim. Keep your accounting records (sales invoices, purchase receipts, bank statements), the tax-adjusted computation showing how the loss was calculated, evidence of commerciality (business plans, marketing activity, client pipeline), and – for share loss relief – share certificates, subscription agreements, and evidence of negligible value (administrator's report, company strike-off notice).

Records must generally be retained for five years after the 31 January filing deadline, but keeping them for six years is safer if a loss is being carried forward.

Worked examples

Trading loss set against prior-year general income

Scenario. Priya starts a freelance graphic design business in 2024/25. Her trading loss (after capital allowances) is £18,000. In 2023/24, she was employed with total income of £52,000.

She claims sideways relief under s 64 against her 2023/24 general income.

Priya originally paid tax on £39,430 of taxable income. The relief saves £18,000 × 40 % = £7,200 (assuming her loss falls entirely in the higher-rate band), refunded by HMRC after she files her 2024/25 return.

Because this is also her first tax year of trade, she could instead use early years relief (s 72) and carry the loss back to 2021/22 or even 2020/21 if doing so yields a higher-rate refund in those years.

Trading loss carried forward

Scenario. Tom, a self-employed carpenter, has an unused trading loss of £12,000 from 2024/25. In 2025/26 his trade produces a profit of £30,000.

Tom's Class 4 NIC is also calculated on £18,000 rather than £30,000, saving both income tax and NIC.

Terminal loss relief on cessation

Scenario. Sarah closes her consultancy on 31 March 2026 (tax year 2025/26). Her terminal loss (final 12 months) is £25,000. Her trading profits in recent years were:

Under terminal loss relief, the £25,000 is set against trading profits of the latest year first:

2025/26 – no profits (cessation loss year). 2024/25 – £8,000 relieved. 2023/24 – £15,000 relieved. 2022/23 – £2,000 relieved (remaining balance). Total relieved: £25,000. Sarah receives refunds for each amended year.

Property loss carried forward

Scenario. James owns a buy-to-let flat. In 2024/25 his rental income is £9,000 and his allowable non-finance expenses (repairs, insurance, management) total £11,500. His mortgage interest is £4,000.

The mortgage interest cannot create or increase the property loss – it is dealt with separately as a 20 % tax credit. The property loss is £9,000 − £11,500 = £2,500, carried forward to 2025/26.

In 2025/26, rental profit (before loss relief) is £3,000. The brought-forward loss of £2,500 reduces this to £500 taxable.

Share loss relief with negligible value claim

Scenario. Anika subscribed £20,000 for shares in an EIS-qualifying company and received 30 % EIS income tax relief (£6,000). The company enters administration in 2024/25, and the shares are now worthless.

Anika makes a negligible value claim. Her allowable loss = £20,000 − £6,000 (EIS relief received) = £14,000. She claims share loss relief against her 2024/25 general income of £60,000, saving £14,000 × 40 % = £5,600 in income tax.

Key rules, caps, and restrictions

Annual loss relief cap

Sideways relief and early years relief are subject to an annual cap: the higher of £50,000 or 25 % of adjusted total income. For most small-business owners with modest other income the £50,000 floor is the binding limit. Losses exceeding the cap can still be carried forward.

Commercial trade and hobby farming

HMRC will deny sideways relief if the trade is not conducted on a commercial basis with a view to profit. The hobby farming rule goes further: if a farming trade has been loss-making for five consecutive years, sideways relief is automatically blocked unless you can demonstrate a realistic expectation of future profit (for example, a structural change to the business model).

Non-active participation and partnership limits

Where a trader or partner devotes fewer than about 10 hours per week to the trade on average, sideways relief is capped at £25,000. For limited partners and certain LLP members, relief is also limited to the capital they have genuinely contributed and have at risk.

Cash basis restrictions from April 2024

Since the cash basis became the default for unincorporated businesses, any loss computed on the cash basis can only be carried forward (s 83). Sideways relief, early years relief, terminal relief, and the CGT election are all unavailable. If you anticipate a loss and want flexibility, elect for accruals on your tax return for that year.

Trading allowance and capital allowances

Claiming the £1,000 trading allowance as an alternative to deducting actual expenses means you cannot create a trading loss – the allowance simply exempts the first £1,000 of income. Capital allowances, by contrast, can create or increase a loss and are often central to early-year loss claims where significant equipment is purchased.

Special situations and planning points

New businesses and early trade loss strategy

In your first four years, you have a unique window for early years relief. Consider whether carrying the loss back to a high-income employment year produces a larger refund than waiting for future trade profits that may be taxed at only the basic rate. Also weigh whether the cash basis (now the default) limits your options – if it does, elect for accruals from the outset.

Ending a business and terminal loss planning

Terminal loss relief only applies to the final twelve months, so the cessation date matters. If bringing forward the closure date by a few weeks changes which tax year the loss falls in, it can alter the carry-back window significantly. Ensure all outstanding invoices, accruals, and capital allowance disposals are properly recorded before filing the final return.

Basis period reform and loss timing

From 2024/25, all unincorporated businesses are taxed on the tax-year basis. The 2023/24 transitional year may have created overlap relief or transition profits that feed into loss computations. If you had overlap relief from earlier years, it was used in 2023/24 and may have created or increased a loss there. Check your 2023/24 return carefully – a missed claim could be worth reclaiming within the amendment window (by 31 January 2026).

Devolved rates vs UK-wide loss rules

Scotland and Wales set their own income tax rates on non-savings, non-dividend income, but the mechanics of loss relief remain UK-wide. A Scottish taxpayer claiming sideways relief still reduces total income in the same way; the saving simply reflects the Scottish rate bands rather than the rUK bands.

💡 Tip: Losses and Universal Credit / Class 4 NIC. A trading loss can reduce your Class 4 NIC liability (because NIC is charged on taxable profits), but be aware that Universal Credit uses a separate "Minimum Income Floor" for the self-employed after an initial start-up period. A large loss claim will not necessarily reduce your UC assessment in the same way it reduces your tax bill. If you are on UC, seek specialist advice before making loss elections that assume a lower income figure will flow through to your benefits calculation.

Avoiding common mistakes and HMRC enquiries

The errors HMRC sees most often are: claiming sideways relief on a cash-basis loss (not permitted from 2024/25), ticking the wrong boxes on the SA103, missing the one-year post-filing claim deadline, including disallowable personal expenses in the loss computation, and attempting to use the same loss twice. HMRC's risk profiling targets loss claims that are disproportionately large relative to turnover, so keep clear records and be ready to justify every figure.

Recent and upcoming changes (2024/25)

Cash basis as the default

From 6 April 2024, the cash basis is the default for all sole traders and partnerships regardless of turnover (the previous £150,000 threshold has been removed). You can still elect for accruals on your SA103 or partnership return. The most important consequence for losses is that sideways relief is unavailable under the cash basis – if this matters to you, elect for accruals.

Basis period reform

The move to the tax-year basis is now complete. Any transition adjustments from 2023/24 should already be reflected in your return. If you had large overlap relief, it may have generated or increased a loss in 2023/24 that can still be claimed (the amendment window closes 31 January 2026). Document your calculations and retain your overlap relief figure from earlier returns.

Property and furnished holiday lettings

The government announced the abolition of the separate FHL tax regime. While 2024/25 broadly retains the existing treatment, changes are expected from 2025/26 that would remove sideways loss relief for FHL businesses and align them with ordinary property income. Landlords relying on FHL loss relief should stress-test their position under both the current and proposed rules and keep detailed records to pivot their claim strategy if necessary.

How income tax losses differ from Corporation Tax and CGT losses

Individuals vs companies

A sole trader and a one-person limited company can have very different loss outcomes even on identical figures. Companies carry back trading losses only one year (or three years for terminal losses), and unused losses carry forward against total profits (not just trading profits). Group relief lets companies share losses with other group members – something unavailable to sole traders. Corporation Tax is a flat rate; income tax has progressive bands, so the value of a loss depends heavily on the individual's marginal rate.

Income tax losses vs CGT losses

Capital losses can only offset capital gains. Income tax losses can only offset income – unless you make the s 71 election to convert a trading loss into a capital loss. Once converted, the loss follows CGT rules and cannot revert. The election is useful when gains are taxed at 20 % (or higher from October 2024) and you have insufficient income to absorb the loss, but think carefully – the conversion is irreversible for that portion of the loss.

Quick-reference glossary

Income tax loss – a shortfall arising when allowable deductions exceed taxable income from a source in a tax year.

Sideways relief – setting a trading loss against general income of the same or previous tax year.

Early trade loss relief – carrying back a loss from the first four years of a new trade against general income of the preceding three years, earliest year first.

Terminal loss relief – carrying back a loss from the final twelve months of a ceased trade against trading profits of the prior three tax years.

Share loss relief – income tax relief for losses on qualifying subscribed shares (including EIS/SEIS shares).

Negligible value claim – a claim to treat shares as disposed of at nil value to crystallise a loss without an actual sale.

Basis period – the period of account whose results are taxed in a given tax year (now aligned to the tax year from 2024/25).

Sources, forms, and where to get help

HMRC helpsheets: HS227 (Losses), HS286 (Share loss relief), HS260 (Overlap relief – useful for basis period reform queries). Legislation: Income Tax Act 2007 Parts 4 and 4A; TCGA 1992 s 131–s 135 for share loss relief. Self Assessment schedules: SA103 (self-employment), SA104 (partnership), SA105 (property), SA108 (capital gains). Online services: HMRC's Personal Tax Account for amending returns; the Government Gateway for filing.

If the amounts are significant, or if your situation involves multiple income sources, partnership structures, or interactions with EIS relief, consider engaging a chartered tax adviser (look for members of the CIOT, ATT, or ACCA). Tax software such as Xero Tax, TaxCalc, or Andica can automate the loss computation, but won't make the strategic decision for you – that is where professional advice earns its fee.

FAQ

Can I split a single trading loss between current year, carry back, and carry forward?

Yes. You can claim part of a loss sideways (against current or prior-year income) and carry the remainder forward. However, the sideways claim itself is all-or-nothing for each year – you cannot restrict it to a specific amount within a single year.

What happens if I miss the time limit for a loss claim?

In most cases, the relief is lost. HMRC has very limited discretion to accept late claims, and only in exceptional circumstances (such as serious illness). Carry-forward relief has no time limit, so the loss is not wasted entirely – but the more valuable sideways and carry-back reliefs will be unavailable.

Do loss claims affect student loan repayments or the High Income Child Benefit Charge?

Sideways relief reduces your net income, which can bring you below the £50,000 HICBC threshold or reduce your Plan 1/2/4 student loan repayment. This is sometimes an overlooked benefit of making a current-year claim rather than carrying forward.

Do Making Tax Digital requirements change how I report losses?

MTD for Income Tax (expected to be mandatory from April 2026 for those above the threshold) changes the reporting frequency – quarterly updates plus a final declaration – but the underlying loss relief rules and claim mechanics remain the same. You will still make the claim through the end-of-year declaration rather than in quarterly updates.