SEG Income and Tax: Do You Need to Tell HMRC?

Why this matters right now

More than 1.6 million UK households now have solar panels, and hundreds of thousands earn money each year through the Smart Export Guarantee (SEG). For most people, this income falls comfortably below HMRC's tax-free threshold. But many homeowners don't realise that SEG income doesn't exist in isolation — it shares a single £1,000 annual allowance with everything else they earn from side activities.

In early 2026, energy industry analysts flagged that an estimated 605,000 UK solar households may be earning more than the trading allowance when you factor in side hustles and other income sources. Around 54,500 of those households faced an automatic £100 fine for missing the 31 January 2026 online self-assessment deadline for the 2024–25 tax year.

This isn't about HMRC targeting solar owners specifically. It's about a tax rule that millions of people misunderstand — and solar export income is one of the ways they tip over a threshold they didn't know existed.

The £1,000 trading allowance — what it is and why it matters for solar owners

HMRC introduced the trading income allowance in April 2017. It gives every individual a £1,000 tax-free allowance each tax year against income from:

• Self-employment or freelance work
• Casual services (babysitting, gardening, odd jobs)
• Hiring out personal equipment
• Selling goods online (eBay, Vinted, Etsy, Facebook Marketplace)
• Solar electricity exported to the grid through the SEG

If your total gross trading income from all of these sources combined is £1,000 or less in a tax year, you generally don't need to report it to HMRC. You don't pay tax on it and you don't need to file a self-assessment return (unless you're required to for another reason, such as being self-employed or having other income above the relevant thresholds).

If your total gross trading income exceeds £1,000, you must register for self-assessment and declare the income. You can then deduct the £1,000 allowance from your income (called "partial relief"), reducing the taxable amount.

A separate £1,000 property allowance also exists

There's a separate £1,000 property allowance for rental income (room rental, property letting). If you have rental income as well as trading income, each gets its own £1,000 allowance. The two don't overlap — but neither allowance can be used to cover the other type of income.

Does SEG income count as trading income?

Based on HMRC guidance, the export payments you receive through the SEG are generally treated as trading or miscellaneous income for domestic solar owners. This puts them into the same pot as your other casual earnings when measuring against the £1,000 trading allowance.

Your savings from self-consumption — the electricity your panels generate that you use directly in your home, avoiding paying for grid electricity — are not income. You're simply using something you generated. These savings don't need to be declared.

What about battery arbitrage income?

If you use a battery to import cheap overnight electricity and export it during peak hours (sometimes called "battery arbitrage"), the position is less clear-cut. HMRC has not issued specific published guidance on this activity as of April 2026. The safer position is to treat any export payments as income regardless of their source, and count them against your £1,000 allowance. If this takes you over the threshold, it would be worth seeking advice from a tax professional or checking directly with HMRC.

Legacy Feed-in Tariff income — how does that fit in?

If you have a pre-2020 solar installation on the old Feed-in Tariff (FiT), you receive two types of payment:

Generation tariff payments — paid for every unit of electricity your system generates, regardless of whether you use it or export it. For domestic owners who installed mainly to cover their own home's needs, HMRC's guidance (set out in the Business Income Manual at BIM40520) states these are generally exempt from Income Tax under S782A of the Income Tax (Trading and Other Income) Act 2005. The exemption applies where the system is installed at domestic premises and you don't intend to generate significantly more than you consume. HMRC uses a rule of thumb that generating more than 20% above your own consumption may indicate a commercial intent that falls outside the exemption.

Export tariff payments — paid for electricity actually sent to the grid. These are treated similarly to SEG payments. For domestic owners within the domestic microgeneration exemption criteria, HMRC guidance suggests these are also likely covered by the same S782A exemption. However, where the exemption doesn't apply (for example, a commercially-sized system), export tariff payments can be taxable.

For most homeowners with a typical domestic FiT installation generating roughly in line with their household consumption, both generation and export payments are generally not subject to Income Tax. The trading allowance becomes most relevant where the domestic exemption doesn't clearly apply, or where you have other trading income alongside.

When you DO need to declare

Here are the scenarios where you should take action:

Your total trading income exceeds £1,000

If your SEG payments plus any other casual/trading income (selling on eBay, freelance work, side services) add up to more than £1,000 in a tax year, you must register for self-assessment by 5 October in the following tax year and file a return by 31 January.

You've been asked to file by HMRC

If HMRC sends you a notice to file a self-assessment return, you must complete it even if you believe your income is below the threshold. Ignoring the notice still results in penalties.

You're already registered for self-assessment

If you're already in self-assessment for other reasons (you're self-employed, you earn rental income above the allowance, you have income from savings or dividends above the relevant limits), you must include your SEG income on your tax return — even if it would otherwise be covered by the trading allowance.

You run a commercial-scale solar operation

If your system is significantly oversized relative to your home consumption, or you're exporting solar income across multiple properties in a business-like manner, different rules may apply and you should seek professional advice.

How to declare — self-assessment basics

If you need to declare SEG or other trading income, the process is:

1. Register for self-assessment at gov.uk/self-assessment-tax-returns. You need to do this by 5 October in the tax year following the one you need to report (e.g., by 5 October 2025 for 2024–25 income).

2. File your return by the deadline — 31 January online (31 October for paper returns, though HMRC strongly encourages online filing).

3. Report your income correctly — SEG export payments are typically reported as miscellaneous income or self-employment income depending on your circumstances. If your gross trading income is above £1,000, you can deduct the trading allowance (£1,000) from the gross figure, rather than claiming actual expenses.

4. Keep records — keep statements from your SEG provider showing your payments, and any other evidence of income received. HMRC can require you to keep records for at least five years after the 31 January deadline for the relevant tax year.

What happens if you don't declare

HMRC has the power to open enquiries into past tax years and charge penalties for undeclared income. The most immediate risk for most solar owners is missing the self-assessment filing deadline:

• Immediate £100 penalty — automatic, applied the day after the deadline even if you owe no tax
• Daily penalties of £10 — applied after three months of non-filing, for up to 90 days (totalling up to £900)
• £300 or 5% of tax due — whichever is higher, applied after six months
• £300 or 5% of tax due again — applied after twelve months

In addition, if HMRC discovers undeclared income through its data-matching programmes (which compare information from energy suppliers, payment processors and other sources), you may face further penalties for inaccuracy or failure to notify, plus interest on any unpaid tax.

Practical steps to take now

Step 1: Find out how much SEG income you received

Log in to your energy supplier's portal or check your paper statements. Your SEG provider is required to send you a summary of payments — many issue these quarterly or annually. Add up all SEG payments received in the tax year (6 April to 5 April).

Step 2: Add up your other trading income

Think honestly about other cash income you've received from casual activities in the same tax year: selling items online, doing odd jobs, freelancing, renting out a car parking space, tutoring, and so on. Add that to your SEG income.

Step 3: Check whether you're already in self-assessment

If you already file a self-assessment return (for example because you're self-employed), you need to include SEG income on it regardless of the amount. If you're not in self-assessment and your total is under £1,000, you generally don't need to take any action.

Step 4: If in doubt, check HMRC's guidance or seek advice

HMRC's trading allowance guidance is the authoritative source. If your situation is complicated — multiple income streams, a large system, export from more than one property — it may be worth speaking to an accountant or tax adviser. Many offer a one-off consultation for a reasonable fee.

Common scenarios at a glance

Note: "eBay selling" above means selling goods for profit as a trade, not occasional selling of personal possessions. HMRC distinguishes between the two.

Key dates and thresholds

• Tax year: 6 April to 5 April (e.g., 6 April 2025 to 5 April 2026)
• Trading allowance: £1,000 per person per tax year (shared across all trading income sources)
• Register for self-assessment: by 5 October following the tax year in question
• File your return (online): by 31 January following the tax year (e.g., 31 January 2027 for 2025–26)
• File your return (paper): by 31 October following the tax year
• Late filing penalty: £100, applied immediately after the deadline
• HMRC contact for general income tax queries: gov.uk/contact/hmrc

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