There are several reasons why you might need to file a self-assessment tax return. This could apply if you are self-employed, a company director, have an annual income over £150,000, or receive income from savings, investments or property.

You must file a self-assessment tax return if any of the following apply to you during the tax year:

• You were self-employed as a sole trader and earned more than £1,000 (before expenses).
• You were a partner in a business partnership.
• Your total taxable income exceeded £150,000 in the 2025–26 tax year. However, even if your income is below £150,000, other factors (such as rental income or capital gains) may still mean you need to file a self-assessment return.
• You had to pay Capital Gains Tax on the sale or disposal of assets.
• You were liable for the High Income Child Benefit Charge.
• You had other sources of untaxed income, such as:
  o Rental income from property
  o Tips or commission
  o Savings and investment income (including dividends)
  o Foreign income

If you are filing a self-assessment return for the first time, you must notify HMRC by 5 October following the end of the tax year. For the 2025–26 tax year (ending 5 April 2026), this means the registration deadline is 5 October 2026.

HMRC provides a helpful online tool to check whether you need to submit a self-assessment return: www.gov.uk/check-if-you-need-tax-return.

The Annual Investment Allowance (AIA) is a generous tax relief that allows for the total amount of qualifying expenditure on plant and machinery to be deducted from pre-tax profits. The maximum amount that can be claimed for the AIA is limited to a £1 million annual cap on qualifying purchases.

The AIA can be claimed by an individual, partnership or company carrying on a trade, profession or vocation, a UK non-residential property business or a furnished holiday let. Only partnerships or trusts with a mixture of individuals and companies in the business structure are unable to qualify for AIA.

The AIA is available for most assets purchased by a business, such as machines and tools, vans, lorries, diggers, office equipment, building fixtures and computers. The AIA does not apply to business cars, items you owned for another reason before you started using them in your business or items given to you or your business.

A claim for AIA must be made in the period the item was bought. This date is defined as the date when a contract was signed, if payment is due within 4 months of the contract being signed. If not, the actual payment date if it is due more than 4 months later.

There are simplified expenses arrangements available for sole traders and business partnerships (with no corporate partner) that allow the use of fixed mileage rates instead of working out the actual costs of buying and running a vehicle (such as fuel, insurance, servicing and repairs). This simplified method is optional, but if you choose to use it for a specific vehicle, you must continue to use it for that vehicle for as long as it is used for business purposes. The simplified expenses regime is not available to limited companies or partnerships involving a corporate partner.

Under simplified expenses, the following flat rates per business mile are available for vehicle costs that are wholly and exclusively for business use:

The number of people in the vehicle does not affect the rates above. The rates are only available for journeys, or any identifiable part or proportion of a journey, that are wholly and exclusively for business purposes. For example, travel from home to work is not a qualifying journey.

The self-employed can continue to claim for other costs not covered by the flat rate for mileage such as parking, tolls, and congestion fees as well as other separate travel expenses such as train journeys.

Automatic enrolment for workplace pensions has helped many employees to start making provision for their retirement with employers and government also contributing to make a larger pension pot.

The law states that employers must automatically enrol workers into a workplace pension if they are aged between 22 and State Pension Age, earns more than minimum earning threshold. The minimum threshold is currently £10,000 and will remain the same in 2026-27. The employee must also work in the UK and not already be a member of a qualifying work pension scheme. Employees can opt-out of joining the pension scheme if they wish.

Under the rules, employers are also required to offer their workers access to a workplace pension when a change in their age or earnings makes them eligible. This must be done within 6 weeks of the day they meet the criteria.

Under the automatic enrolment rules the employer and the government also add money into the pension scheme. There are minimum contributions that must be made by employers and employees.

Both the employer and employee need to contribute. There is a minimum employer contribution of 3% and employee contribution of 4%. This means that contributions in total will be a minimum of 8%: 3% from the employer, 4% from the employee and an additional 1% tax relief. For example, if you pay £40, your employer adds £30, and you receive £10 in tax relief, a total of £80 goes into your pension.

In most automatic enrolment schemes, employees make contributions based on their total earnings between £6,240 (the lower qualifying earnings limit) and £50,270 (the upper qualifying earnings limit) a year before tax. This means that for many employees the 8% contribution rate will not be based on their full salary.

A claimant made allegations of unfair dismissal, discrimination, and detriment resulting from whistleblowing. While his claim against the Council was subsequently withdrawn early on, the claim against the private limited company proceeded.

The respondent, however, argued that the claimant was a volunteer and that his claims were vexatious, threatening to apply for a strike-out order and a costs award in the range of £2,500 to £3,000, although the case was postponed due to bereavement. The conflict escalated when the claimant sent two emails to the Tribunal, the first expressing extreme concern over the respondent’s costs warning, stating that, in the absence of certainty regarding the maximum costs the Tribunal might award, he was considering withdrawing his claim. Later that afternoon, after receiving no reply, he sent a second email declaring that he wished to confirm the withdrawal of his claim unless the Tribunal assured him that no costs order would be made against him.

However, the Tribunal’s internal processing of these emails was disorganised, and the Employment Judge, having seen only the first email, correctly identified it as a potential tactical withdrawal and invited the claimant to clarify his position within 14 days. However, a staff member who had seen the second email, but not the first, sent a letter treating the claim as having been fully withdrawn and cancelled the upcoming hearing, although the claimant had since explicitly stated that he wished to continue with his claim. The chaos continued with the Tribunal asserting that the claim had been unambiguously withdrawn and could not be resurrected.

However, the Appeals Tribunal ruled in favour of the claimant as he had made his intent to withdraw conditional upon receiving advice or guarantees regarding potential costs. This ruling means that employers and respondents can no longer immediately rely on a frustrated or conditional email from a claimant as a “get out of jail free” card. Thus, in future cases, Judges are expected to be more interventionist when an unrepresented party suggests they want to drop a claim due to fear or pressure rather than through a genuine desire to end the pursuit of justice.

This case marks a potential end to the prevalent tactic of sending “warning letters” over potential costs to pressure claimants into dropping ‘weak claims’. While these letters are legally valid and often necessary, the bar for such tactics has now been raised, and respondents should be wary of using the threat of costs to trigger an automatic procedural win, as judges may now be more sympathetic to those in financial distress.