Tax is one of the areas where new business founders in London feel least confident, and understandably so. The rules are detailed, they change periodically, and the consequences of getting something wrong can range from a minor correction to a significant penalty. Many of the most common tax mistakes made by new founders are entirely avoidable with the right support in place from the beginning. A small business accountant who understands both the rules and the specific circumstances of a new business can prevent these errors before they happen, rather than fixing them after the fact.
Failing to register for the correct taxes at the correct time is one of the most frequent mistakes new founders make. This includes missing the three-month window to register for corporation tax after starting to trade, delaying VAT registration past the point turnover crosses the threshold, or forgetting to register as an employer before running the first payroll. Each of these has specific deadlines that are easy to overlook when a founder is focused on winning clients and building the business itself. A small business accountant tracks these obligations proactively rather than waiting for the founder to ask.
Misunderstanding allowable expenses leads to two opposite but equally problematic outcomes: either claiming too little out of excessive caution, which means paying more tax than necessary, or claiming things that are not actually allowable, which creates risk if HMRC ever reviews the return. Common areas of confusion include the treatment of home office costs, the rules around entertaining clients, which is generally not deductible even though it feels like a legitimate business cost, and the correct way to claim for a vehicle used partly for business and partly for personal purposes. An accountant clarifies these grey areas accurately.
Getting the salary and dividend split wrong is a mistake specific to limited company directors, and one that can have a meaningful impact on the overall tax bill. Paying too much salary can trigger unnecessary National Insurance contributions, while paying dividends without properly considering the company's available profits or the personal tax implications at higher income levels can create problems of its own. Fred Michael & Co works with directors to structure this split in a way that reflects both the company's financial position and the individual's personal tax circumstances, reviewing it periodically rather than setting it once and forgetting about it.
Missing out on valuable reliefs is another common and costly oversight. The Annual Investment Allowance can allow significant tax relief on qualifying equipment purchases in the year they are made, but founders unaware of it sometimes spread the cost unnecessarily across multiple years instead. Similarly, businesses doing genuinely innovative work sometimes fail to realise they may qualify for R&D tax relief, missing out on a potentially substantial benefit simply because nobody flagged that their activities might qualify. A small business accountant actively looks for these opportunities rather than waiting for a founder to ask about them by name.
Poor timing of income and expenditure around the tax year end is a subtler mistake, but one that can affect the tax bill meaningfully. Bringing forward a planned equipment purchase by a few weeks, or delaying an invoice by a similar margin, can sometimes shift which tax year a cost or income falls into in a way that benefits the business, depending on its specific circumstances. Founders without accounting support rarely think about timing in this way, simply transacting as things naturally occur rather than considering whether a small adjustment in timing could improve the outcome.
Underestimating the total tax liability and failing to set money aside is perhaps the most financially damaging mistake of all, because it creates a cash flow crisis precisely when the bill becomes due. New founders sometimes treat all incoming revenue as available to spend, only to realise months later that a significant corporation tax or self-assessment payment is due and the funds are not there. A small business accountant helps establish realistic estimates of tax liability early and recommends setting aside funds consistently, so the eventual payment is never a surprise that threatens the stability of the business.
Filing returns late, or filing them accurately but forgetting to actually make the corresponding payment on time, both trigger penalties and interest that are entirely avoidable with proper organisation. It is a common misconception that submitting a return on time is sufficient, when in fact payment deadlines can differ from filing deadlines and both need to be met. An accountant keeps track of both sets of deadlines and ensures the founder knows exactly what needs to happen and by when, removing the risk of an accidental late payment due to simple confusion about dates.
Making decisions based on outdated tax knowledge is a mistake that even well-intentioned founders fall into, particularly if they read general advice online that does not reflect the current rules or their specific situation. Tax rules change periodically, sometimes significantly, and advice that was accurate a few years ago may no longer apply. A small business accountant stays current on these changes as part of their professional responsibility, ensuring the guidance a founder receives reflects the actual current rules rather than something that may have shifted since it was first read somewhere online.
Every one of these mistakes is common, understandable, and entirely avoidable with the right support. Fred Michael and Co works with new founders across London specifically to prevent these errors before they occur, providing proactive guidance rather than simply reacting to problems once they have already developed. For any founder feeling uncertain about their tax position, addressing that uncertainty early with professional support is almost always far cheaper than the cost of the mistakes it prevents.
A less obvious but still common mistake is failing to keep adequate records to support claims already made on a tax return, even when the claim itself was legitimate. HMRC can request evidence for expenses or reliefs claimed well after a return has been filed, sometimes years later, and a founder who cannot produce supporting documentation risks having a valid claim disallowed simply because the paperwork was not retained properly. A small business accountant sets up systems that keep records organised and accessible for the required retention period, so that if a query ever does arise, the necessary evidence can be produced quickly and confidently rather than triggering a stressful scramble.
New founders sometimes also assume that because their business is small, HMRC is unlikely to ever take a close interest in their affairs, and let their record keeping and compliance standards slip as a result. This assumption is risky, since compliance checks can affect businesses of any size, and the consequences of poor records extend beyond just the specific query at hand, potentially undermining confidence in the accuracy of other returns as well. Fred Michael and Co encourages every client, regardless of size, to maintain the same standard of accurate, well-supported record keeping, precisely because the size of a business today says little about whether it might face a compliance query in the future.
Taken as a whole, these avoidable errors share a common thread: they arise from acting on assumptions rather than verified advice, which is exactly the gap that proper accountant support closes for founders in their earliest and most vulnerable trading years, turning what could have been a string of expensive lessons into a smooth and confident start.
Starting or Growing a Business in London?
Let's set your business up the right way
Fred Michael & Co Ltd supports small businesses and startups across London with business planning and financial advice from day one.