You would think that sending your self assessment tax return would be a straightforward process—log in, enter some numbers, send. But year in, year out, thousands of people get it wrong. From filing late to reporting the wrong income, these mistakes more often than not result in penalties, anxiety, and even HMRC enquiries.
If you’re new to self assessment, or if you’ve completed it before but never really felt 100% sure, this article is the one for you. Here, we’ll examine some of the most common myths and what you should actually be doing.
Myth #1: “HMRC Will Tell Me If I Need to File”
Nope. HMRC will send you a notice to file, but if you have income that is not PAYE—like rental income, freelance income, or dividends—then it’s your responsibility to register and submit a return.
Most think that they’re flying under the radar, only to receive a letter from HMRC months (or years) later. If you earn more than £1,000 in self-employment or have previously untaxed income, it would be wise to double-check if you must file before the deadline approaches.
Misconception #2: “I’ll File Later—There’s Still Time”
The online return deadline is 31st January. Don’t leave it till the last minute, though. If you haven’t already registered with HMRC, it could take days to get your login details. And even when you have logged on, you will need time to sort out documents, double-checking numbers, and checking that it all balances.
And don’t forget: the 31st January deadline is not just for submitting the return but also for your tax bill. Miss it, and you’re in for a £100 fine, with more adding up daily if the delay continues.
So, What Should You Do?
Make an early start—even if your income isn’t fully in yet. You can begin gathering your documents, estimate your liability, and familiarise yourself with the online portal. The sooner you start, the greater the likelihood of finding any corrections or inquiries.
Don’t know where to start? Helpful tip: round up your P60 or P45, bills, bank interest statements, dividend vouchers, and any other expense or income-related papers from last year. Sort them out early, not later.
Claiming Expenses? Know What Is Allowed
Another common mistake? Either claiming too much or too little on expenses. For example, claiming the entire phone bill as a business expense where you also use it for personal use might be viewed with suspicion.
On the other hand, most of us remember that they can claim for home-office use, software subscription, or mileage. Being aware of what you can claim can lower your tax bill—but you will have to provide receipts as evidence.
Bonus Tip: Think about “Payments on Account”
If it’s your first time and your tax bill is more than £1,000, HMRC will probably request payments on account—a prepayment of next year’s tax. New filers are often caught by surprise because of this unexpected second payment in July.
Pre-planning can avoid costly burdens in the future. It’s best to plan ahead rather than be stressing halfway through the year when HMRC issues a reminder.
Want To Eliminate Stress Entirely?
Here’s the truth: it’s totally possible to file your own tax return—but not necessarily a good idea. If you have a straightforward financial life, sure. But if you have many income streams, foreign income, or if you’re just afraid of doing it right, paying an accountant will pay for itself in time and dollars.
They can help you get the most out of your return, stay compliant, and even discover tax-saving strategies you might not know about.
The Takeaway: Don’t Wing It
Your self assessment tax return is not something to put off until the eleventh hour or rush through. Tackle it like what it is—a vital part of staying in HMRC’s favour. The more careful you are, the less chance you’ll have of being penalised, paying more in tax than you need to, or missing out on reliefs that are rightfully yours.
So if you’re going to file soon, begin early, double-check everything, and seek assistance if you need it. You’ll be glad you did.
