A self assessment tax return is rarely difficult because of one single figure. Problems usually arise because income has come from several places, records are incomplete, or a deadline has been left until January. For company directors, sole traders, landlords and higher-income taxpayers, getting the return right means more than avoiding penalties. It is an opportunity to understand your tax position early and make better decisions for the year ahead.

Who needs to complete a self assessment tax return?

Not everyone who pays tax needs to file a return. Employees whose only income is taxed through PAYE will often have nothing further to submit. However, the position changes when income, gains or reliefs sit outside straightforward employment.

You will commonly need to register for self assessment if you are self-employed and your gross trading income exceeds the £1,000 trading allowance, a partner in a business partnership, or a company director. Many landlords also need to file, particularly where rental profits have not been dealt with through PAYE. HMRC may require a return where you have received significant investment income, made taxable capital gains, claimed certain tax reliefs, or have paid too little tax through another route.

There are exceptions and thresholds, so it is sensible not to make assumptions based on a friend’s or colleague’s circumstances. For example, a director with no salary, dividends or other untaxed income may have a different filing position from a director drawing a mixture of salary and dividends. If HMRC has issued a notice requiring a return, it must be completed or formally withdrawn, even where you believe no tax is due.

Self assessment deadlines that matter

The tax year runs from 6 April to 5 April. For the 2025/26 tax year, which ended on 5 April 2026, the usual deadlines are 5 October 2026 to tell HMRC if you need to register for the first time, 31 October 2026 for a paper return, and 31 January 2027 for an online return.

The 31 January deadline is also normally the date by which you must pay any tax owed for the previous tax year. Filing early does not mean paying early if you would rather retain cash until the payment date, but it does give you clarity. You can budget for the liability, check whether a payment on account is due, and avoid trying to resolve missing figures in the final days before the deadline.

Late filing can trigger an automatic penalty even if you have no tax to pay. Interest and further charges may follow where payment is late. More importantly for a business owner, last-minute filing turns what should be useful financial information into a rushed compliance task.

Do not overlook payments on account

A common surprise is the payment on account system. If your self assessment bill is more than £1,000 and less than 80% of your tax was collected at source, HMRC will usually ask for advance instalments towards the following year’s bill.

These are generally paid on 31 January and 31 July. The first January payment can therefore include the balancing payment for the year just ended plus the first instalment towards the next year. This can feel like a steep bill, especially for a growing sole trader, landlord or consultant whose profits have risen.

Where income has genuinely fallen, it may be possible to reduce payments on account. Care is needed: reducing them too far can lead to interest if the final liability is higher than expected. A realistic profit forecast is far better than an optimistic guess.

Records turn a tax return into a manageable job

Good records are not just for your accountant or for HMRC. They show whether the business is producing the cash and profit you expected. Waiting until the end of the year to sort bank statements, invoices and receipts makes it harder to spot missed income, duplicate costs or opportunities to plan ahead.

For self-employed people, separate business banking and regular bookkeeping make a substantial difference. Keep sales invoices, purchase receipts, bank records, mileage details where relevant, and evidence of any expenses claimed. Landlords should retain letting statements, repair invoices, mortgage interest information and details of periods when a property was vacant.

Directors should ensure that salary, dividends, benefits and company expenses are recorded correctly. A personal payment made from the company bank account is not automatically a deductible business expense, and the treatment may affect the director’s loan account as well as the company tax position.

HMRC generally expects self assessment records to be retained for at least five years after the 31 January submission deadline for the relevant tax year. Digital records are convenient, but receipts and documents still need to be clear, complete and accessible if questions arise later.

Claiming expenses without creating unnecessary risk

Tax relief is available for expenses incurred wholly and exclusively for your trade or business. That principle is simple, but applying it can require judgement. A laptop used entirely for work is different from a broadband bill, mobile contract or vehicle used for both business and personal purposes.

For mixed-use costs, only the business element should normally be claimed. Being realistic here protects you if HMRC reviews the return. It also gives a truer picture of business profitability, which is particularly valuable when setting prices, considering recruitment or applying for finance.

Some costs are often missed because they are paid personally rather than from the business account. Professional subscriptions, business insurance, accountancy fees, use of home expenses and mileage may all be relevant depending on the facts. Equally, some payments that feel business-related are not deductible in full, or are dealt with under different rules. Capital purchases, entertaining and clothing are familiar areas where a quick assumption can be costly.

The best approach is not to chase every possible deduction. It is to claim the reliefs you are entitled to, supported by sound records and a clear explanation.

Give yourself time to plan, not just file

A return prepared after the year end records what has happened. Prepared early enough, it can also support planning. Knowing your expected taxable income before the end of the tax year may help you decide whether pension contributions, charitable donations, dividend timing or capital expenditure should be considered.

The right action depends on your wider position. A company owner may need to balance personal tax, corporation tax, cashflow and the amount left available for investment in the business. A landlord may be weighing repairs against improvements, while a self-employed professional may need to set aside more money for tax as profits increase. There is no single tax-saving measure that suits everyone.

This is why bookkeeping, accounts and personal tax should work together. Up-to-date information creates choices. Historic information, produced months late, usually does not.

Common self assessment mistakes to avoid

The most expensive errors are often ordinary ones: omitting bank interest or dividend income, claiming private expenditure, forgetting a source of rental income, or entering figures from estimates rather than final documents. Another frequent issue is treating money received as profit without allowing for costs, tax and upcoming payments on account.

It is also worth checking that the return reflects the correct tax year. Income and expenses do not always follow the date money reaches a bank account, particularly for businesses preparing accounts on an accruals basis. If you are unsure, asking before submitting is normally easier than correcting a return afterwards.

For clients with several income sources or changing circumstances, professional preparation provides more than an extra pair of hands. It brings a structured review of the figures, an explanation of what is due and when, and practical advice that fits the wider financial picture. RK & Co can prepare self assessment returns with fixed fees agreed in advance, while helping clients use their numbers to plan with greater confidence.

The most useful time to think about your next return is not the week before 31 January. Put records in order now, set aside money regularly, and deal with questions while there is still time to make a considered decision.

For many married couples and civil partners, the simplest way to claim Marriage Allowance to save tax is also one of the most frequently missed. It is not a complicated relief, but it does depend on the right combination of incomes. Where one partner has unused Personal Allowance and the other pays tax at the basic rate, a claim can reduce the household’s tax bill by up to £252 a year.

That may not transform a business cashflow forecast on its own, but tax planning often works best when practical savings are not left behind. Marriage Allowance is particularly relevant for families where one person works part-time, takes time away from work, runs a small side business or has recently retired.

What is Marriage Allowance?

Marriage Allowance lets one spouse or civil partner transfer part of their unused Personal Allowance to the other. The Personal Allowance is the amount of income someone can normally receive before paying Income Tax.

The transfer is currently £1,260. It does not mean the recipient gets an extra £1,260 tax-free in the usual sense. Instead, it gives them a tax reduction worth up to 20% of that amount – currently up to £252 for the tax year.

The partner making the transfer gives up that portion of their own allowance. Their tax-free allowance is therefore reduced by £1,260, while their spouse or civil partner receives the corresponding tax benefit.

For a couple where the transferring partner has little or no taxable income, this is usually a straightforward household saving. Where their income is close to the Personal Allowance, it is worth checking the numbers before applying.

Who can claim Marriage Allowance to save tax?

You must be married or in a civil partnership. Couples who live together but are not married or civil partners cannot claim, regardless of how long they have shared a household.

The person transferring allowance will normally need income below the standard Personal Allowance, currently £12,570. This could include employment income, self-employment profits, pension income, rental income and certain taxable benefits.

The receiving partner must pay Income Tax at the basic rate. For most taxpayers in England, Wales and Northern Ireland, this generally means their income falls between the Personal Allowance and the higher-rate threshold. Scottish taxpayers have different Income Tax bands, but Marriage Allowance can still be available where the receiving partner is a starter, basic or intermediate-rate taxpayer.

The allowance is intended for couples born on or after 6 April 1935. If either partner was born before that date, Married Couple’s Allowance may be the relevant relief instead. It works differently and should not be confused with Marriage Allowance.

Eligibility is assessed individually, so business owners should take particular care. A director’s modest salary may suggest that they qualify to transfer allowance, but dividends, rental profits, bank interest or other income can change the result. Equally, a self-employed person may have low profits in one year and higher profits in the next.

A simple example

Suppose Alex has income of £8,000 and Morgan has a salary of £30,000. Alex has unused Personal Allowance and can transfer £1,260 to Morgan. Morgan is a basic-rate taxpayer, so the transfer can reduce Morgan’s Income Tax by £252.

The result is a full household tax saving of £252 because Alex’s income remains comfortably below the reduced allowance.

Now consider a different position. If Alex earns £12,200, transferring £1,260 reduces Alex’s allowance to £11,310. Alex may then pay tax on part of their income. Morgan can still receive the tax reduction, but the overall household gain will be lower. The claim may still be worthwhile, but it should be calculated rather than assumed.

How to make a Marriage Allowance claim

The partner with the lower income makes the application through HMRC. In most cases, the claim can be made online using both partners’ National Insurance numbers and identification details.

Once HMRC accepts the application, the tax benefit is usually reflected through the receiving partner’s PAYE tax code. If they complete a Self Assessment tax return, the relief may instead be dealt with through the tax calculation.

A claim normally continues in future tax years unless the couple’s circumstances change or it is cancelled. That makes it convenient, but it also means it should be reviewed. A promotion, a profitable trading year, new rental income or a dividend payment can mean the transferring partner no longer has sufficient unused allowance.

If you are already completing Self Assessment, include the relevant information accurately and retain records of the income figures used. For directors and self-employed taxpayers, the right answer is based on total taxable income, not simply the salary paid from a company or the money withdrawn from a business bank account.

Do not overlook backdated claims

One of the most useful features of Marriage Allowance is that eligible couples can usually backdate a claim for up to four previous tax years. The amount available depends on the allowance and tax position in each of those years, so it will not necessarily match the current maximum.

Backdating can be valuable where a couple did not know the relief existed, or where one partner had a period of lower income due to parental leave, part-time work, illness, retirement or a change in business circumstances. HMRC will consider the historic eligibility conditions for each year claimed.

This is also where a quick review can prevent disappointment. If the higher-earning partner was a higher-rate taxpayer in a previous year, that year may not qualify even if the couple qualify now. Similarly, income that was overlooked at the time, such as dividends or property income, can affect the result.

When Marriage Allowance may not be the best answer

Marriage Allowance is valuable, but it is not automatic tax planning for every couple. The key trade-off is the transferor’s reduced Personal Allowance.

It may be less attractive when the lower-earning partner’s income sits just below £12,570. They may have some tax to pay after the transfer, reducing the net saving for the couple. It can also be unsuitable if their income is likely to rise during the year, perhaps because a sole trader expects a stronger final quarter or a company director plans to take additional dividends.

There can be practical administration to consider too. If PAYE codes are wrong or income changes mid-year, the tax position may be corrected later through PAYE, Self Assessment or an HMRC calculation. That does not usually remove entitlement, but it can affect when the benefit is received.

For couples with more complex income, Marriage Allowance should be considered alongside the wider position. Pension contributions, dividend planning, salary levels, property income and the timing of capital gains can all influence Income Tax. The best approach is not to chase a single relief in isolation, but to make sure the household’s allowances and tax bands are working together.

A practical check for business owners and families

Before applying, look at each partner’s expected taxable income for the year. Include employment income, business profits, dividends, pensions, rental profits and taxable savings where relevant. Then consider whether the lower-income partner will remain below their reduced allowance after the transfer.

This check is particularly useful after a change in circumstances. Starting a new role, ceasing self-employment, taking maternity or paternity leave, retiring, drawing a pension or altering a company remuneration strategy can all create an opportunity – or remove one.

At RK & Co, we regularly find that personal tax savings are easier to identify when they are reviewed alongside business accounts and future plans, rather than only when a tax return is due. A short conversation before the year-end can be more useful than discovering an avoidable tax cost afterwards.

If your income has changed, take a few minutes to check whether Marriage Allowance fits your circumstances. Small, timely decisions can leave more of your household income available for the plans that matter to you.

A cashflow turnaround example is often more useful than a set of generic finance tips, because the problem rarely begins with one dramatic mistake. For many owner-managed businesses, cash pressure builds quietly: a few late-paying customers, stock bought ahead of demand, a quarterly VAT payment and a growing wage bill can quickly leave a profitable business short of money in the bank.

The good news is that a cashflow problem can usually be understood and improved. It requires clear information, prompt decisions and a plan that protects both customer relationships and the long-term health of the business.

A cashflow turnaround example: a growing Manchester business

Consider a fictional Greater Manchester wholesaler with annual sales of £1.8 million. The company was trading profitably and had a healthy order book, yet its bank balance had fallen from £110,000 to less than £15,000 over six months. The directors had begun delaying their own drawings and were concerned about meeting payroll, VAT and supplier payments.

At first glance, the issue appeared to be falling profitability. A closer review showed something different. Sales had grown by 22%, but average customer payment time had stretched from 32 days to 58 days. The business had also increased stock levels to avoid supply disruption, while agreeing to pay several key suppliers within 30 days. In effect, it was funding customers for nearly two months while paying for goods much sooner.

This distinction matters. Profit is an accounting measure over a period. Cashflow is about the timing of money entering and leaving the business. A company can make a profit on paper and still face a serious cash shortage.

Starting with a realistic view of the position

The first step was not to cut every cost or chase every customer aggressively. It was to establish the facts. The directors prepared a rolling 13-week cashflow forecast, updated weekly, showing expected receipts, payroll, VAT, rent, supplier commitments, finance repayments and other regular outgoings.

The forecast revealed a likely low point of £42,000 overdrawn in week eight if nothing changed. That gave the directors a specific problem to solve, rather than a general feeling that cash was tight. It also showed that the business did not need permanent borrowing of £100,000, as initially feared. It needed a controlled short-term improvement in working capital and a better way to manage cash thereafter.

Good forecasts are not about pretending every figure is certain. They should show the best information available, identify assumptions and be revised as invoices are paid, orders change or costs arise. For a smaller business, a straightforward spreadsheet can be enough if it is maintained properly. For a growing company with more complex transactions, accounting software and regular management reporting can provide a clearer, faster view.

The practical actions behind the turnaround

The business took several actions at the same time, each selected for its likely impact and practicality.

First, it reviewed the sales ledger invoice by invoice. The £310,000 owed by customers was not all equally recoverable. Some invoices were only a few days late; others had been disputed because delivery notes or purchase order references were missing. A small number of customers had simply become used to paying later than agreed.

The finance team sent clear statements, corrected administrative errors and contacted larger overdue customers personally. The conversations were professional rather than confrontational. Where a genuine query existed, it was resolved quickly. Where payment dates had slipped without good reason, the business asked for a firm date and followed up. Within four weeks, it collected £96,000 of overdue debt that had not been included in the directors’ immediate cash expectations.

Second, the company changed its invoicing process. Invoices were issued on the day goods were dispatched rather than at the end of the week. Each invoice included the correct purchase order number and named contact, reducing the chance of avoidable delay. New customers were subject to credit checks, and larger first orders required a deposit or pro-forma payment where commercially appropriate.

Third, the directors examined stock. They found that several slow-moving lines represented £70,000 of cash tied up on shelves. Not every item could be reduced immediately without risking sales, but purchasing was adjusted to reflect actual demand. Obsolete stock was sold through at a controlled discount. This was not ideal for gross margin, but holding stock indefinitely was more damaging to cash and carried a risk of further write-downs later.

Fourth, they spoke to key suppliers before payments became overdue. The company explained its plan and agreed temporary extended terms on selected orders. This was handled carefully. A supplier that is central to your operation should not be treated as a free source of finance without communication. Early discussion can preserve trust; silence followed by missed payment dates can damage it.

Finally, the directors reviewed discretionary spending and capital purchases. A planned vehicle replacement was postponed for three months, and a software subscription that duplicated existing functionality was cancelled. They avoided indiscriminate cost-cutting in areas that supported sales, service quality or operational efficiency. Reducing costs can help, but cutting the wrong expenditure may weaken the business just when it needs to trade well.

The result after 13 weeks

By week eight, the forecast low point had been avoided. The business remained within its existing banking facilities, paid staff and HMRC on time, and finished the 13-week period with a cash balance of £68,000. More importantly, its average customer payment time had reduced to 39 days and stock purchasing was aligned more closely with sales patterns.

The turnaround did not come from one clever funding product or a last-minute rescue. It came from turning financial records into practical actions: collecting what was already owed, improving invoice discipline, reducing unnecessary stock, managing supplier expectations and monitoring the position every week.

There were trade-offs. Discounting old stock reduced margin, while tighter credit terms meant one prospective customer chose another supplier. However, the directors were able to make these choices deliberately. They were no longer making decisions based solely on the bank balance at the end of the day.

What this cashflow turnaround example can teach your business

The precise actions will depend on your sector, margins and customer base. A construction firm may need to focus on stage billing, retention and project cost control. A professional services business may benefit most from requesting upfront payments or recurring monthly billing. A retailer may need to concentrate on stock turns and card settlement timings.

However, the underlying questions are consistent. How long does it take customers to pay? Are invoices accurate and issued promptly? Which costs are fixed, and which can be adjusted? Is stock or work in progress tying up cash? When are tax liabilities due? And does the business have a forward-looking forecast rather than relying on historic accounts?

It is also worth separating temporary cash pressure from a deeper viability issue. If sales are loss-making, margins have eroded or debts are unlikely to be collected, better credit control alone will not solve the problem. The forecast should be paired with a review of profitability by customer, product or service line. That is where management accounts and regular adviser support can make a meaningful difference.

Make weekly cash management a normal habit

Once cash has improved, it is tempting to stop forecasting. That is how the same pressures return. A simple weekly review of bank balances, expected receipts, upcoming payments and major commitments gives directors time to act before a gap becomes urgent.

For owner-managed businesses, this need not become a burdensome exercise. The aim is clarity: know what is due, know what is owed, and understand the decisions that will affect cash over the next few months. RK & Co helps businesses turn bookkeeping, accounts and forecasts into practical and simple advice, so financial decisions can support growth rather than create unnecessary worry.

A cashflow turnaround begins when you replace assumptions with a clear view of the numbers. With timely action and regular review, a difficult period can become the point at which your business gains stronger control and greater confidence.