Self Assessment Simplified: 7 Common Mistakes and How to Avoid Them

Filing your Self-Assessment tax return can be stressful, especially if you’re self-employed or running your own business. Mistakes are easily made but can lead to penalties, unnecessary costs, and headaches. Here’s our guide to the seven most common Self-Assessment mistakes – and how to avoid them!

1. Waiting Until the Last Minute

Procrastination leads to rushed returns and higher risk of errors. Start early, gather your documents in advance, and give yourself time to double-check everything. Early submission reduces stress and increases accuracy.

2. Missing Allowable Expenses

Many self-employed individuals overlook legitimate business expenses that can reduce their tax bill. Commonly missed expenses include home-office costs, travel mileage, software subscriptions, and professional training. Track these expenses consistently to maximise your deductions.

3. Poor Record Keeping

Clear, accurate record keeping is crucial. Poorly kept records can lead to missed expenses or income inaccuracies. Invest in simple accounting software or apps, and regularly update your records to make year-end filing smoother.

4. Misunderstanding Tax Deadlines

Missing HMRC deadlines can be costly. Key dates:

• Online tax return submission: 31st January.
• Second payment on account: 31st July.

Mark these dates clearly in your calendar and consider reminders or alerts to stay on track.

5. Incorrectly Declaring Income

All sources of income must be declared – including side jobs, freelance projects, or rental income. Accurate reporting helps avoid HMRC investigations or penalties. Review all bank statements carefully to ensure nothing is missed.

6. Ignoring HMRC Communications

Ignoring HMRC letters or notifications is risky. Always respond promptly to avoid fines or investigations. Keep all correspondence organised and seek advice if you’re unsure how to respond.

7. Trying to Do Everything Alone

Tax rules are complex and constantly changing. Professional advice often saves more than it costs by maximising deductions, ensuring compliance, and reducing stress. Don’t hesitate to seek guidance from a qualified accountant.

Need Help?

At Crossley & Davis, we’re here to help you avoid Self-Assessment mistakes, ensuring accuracy and peace of mind. Contact us today for a free initial consultation and take the stress out of tax season!