For entrepreneurs who use the same car for work and in their daily lives, transport costs can quickly become difficult to manage. A morning trip to a client might be followed by a stop at the supermarket, a delivery and the journey home, and by the end of the week, fuel, parking and maintenance costs have mounted up without it being clear which expenses are business-related. Separating personal transport expenses from business ones (Separating personal and business) results in more accurate financial records, simplifies bookkeeping and helps business owners understand exactly how much their business costs.
Which journeys count as business travel
Business transport expenses are the costs of journeys made for legitimate business purposes, such as visits to clients, the transport of materials, deliveries and journeys between company premises. Personal errands, family outings and the regular commute between home and the permanent place of work are generally not deductible transport expenses. These distinctions must be understood before recording vehicle expenses or preparing tax documents.
The situation becomes more complicated when a journey combines business and personal activities. An entrepreneur might, for example, drive 15 miles to a supplier and then stop at the supermarket on the way home; the business-related portion must be separated from the additional distance travelled for personal purposes. Accurate records of journeys prevent confusion when verifying expenses at the end of the month.
Keeping track of business mileage from the outset
The mileage log is the basis for distinguishing between business and personal use of the vehicle. Rather than estimating distances after a few months, entrepreneurs should record their journeys as they go. Mobile apps can automatically log journeys, whilst a spreadsheet or a handwritten log remain alternatives for those who prefer manual record-keeping. Regardless of the method, the information must clearly indicate the business purpose of each journey.
An effective mileage log should include:
- Date of journey: when the journey took place.
- Points of departure and arrival: the locations between which the journey was made.
- Business purpose: the reason for the journey.
- Distance travelled: business miles, recorded based on odometer readings or another reliable method.
- Supporting information: meeting confirmations, delivery documents or relevant receipts.
A consultant who travels 12,000 miles in a year, 7,200 of which are for business purposes, uses their car for business 60 per cent of the time, and this proportion forms the basis for allocating eligible expenses using the actual expenses method. Without accurate records, the calculation becomes much more difficult. Keeping a consistent record of distances also helps entrepreneurs understand the transport needs of each project.
Personal travel expenses, kept separate
Entrepreneurs who use the same vehicle for both business and personal purposes need a clear system to distinguish between the two. Weekend trips, family holidays, shopping trips and other personal journeys must be kept separate from the business’s transport records. Even when the vehicle serves both purposes, accurate mileage logs and payment records prevent personal expenses from being mistakenly classified as business expenses.
Personal journeys incur their own transport costs, particularly for those who frequently drive long distances or go on family trips. As well as comparing fuel prices and planning efficient routes, some drivers choose to apply for a fuel credit card (apply for a gas credit card), to earn rewards on personal refuelling. Before applying, it is worth checking the interest rates, fees and terms of the rewards programme to see if the card suits your driving habits. Keeping these payments separate from business transactions makes it easier to manage household travel expenses without complicating the company’s accounts.
Choosing the right method for vehicle expenses
The US tax authorities (IRS) generally allow self-employed individuals who meet the eligibility criteria to calculate deductible vehicle expenses either using the standard mileage rate or the actual expense method, subject to specific rules. The standard mileage rate method uses a fixed amount for each eligible business mile, whilst the actual expense method takes into account eligible operating costs attributable to business use. The two methods follow different rules, so business owners need to be aware of their options before preparing their tax returns, and the choice also affects the supporting documents that must be kept.
Under the actual expenses method, eligible costs may include fuel, repairs, insurance, registration fees and depreciation or lease payments, allocated in proportion to business use. The standard rate method simplifies the calculation, although parking and road tolls relating to eligible business travel can generally be deducted separately. The same operating expenses cannot be deducted twice by combining the two methods for the same distances. Consulting a qualified tax specialist helps to ensure that the chosen method complies with IRS requirements.
What has changed for the 2026 tax year
For 2026, the IRS has set, via a notice published on 29 December 2025, a standard rate of 72.5 cents for every mile travelled for business purposes, which is 2.5 cents more than in 2025. The rate applies to cars, estate cars, pick-up trucks and vans, and its use remains optional. However, the rules for choosing the method have long-term consequences, which many guides overlook. For an owned vehicle, the standard rate must be chosen in the first year the car is used for business purposes, and in subsequent years the owner may choose between the two methods. For a leased vehicle, the choice of the standard rate applies for the entire duration of the contract, including any extensions. The decision made in the first year therefore determines the options available for years to come.
The documentation rules explain why the mileage log matters more than it might seem. Under US tax law, cars fall into the category of assets for which a deduction requires adequate records or sufficient evidence to support the taxpayer’s claims, in accordance with Section 274(d) of the Internal Revenue Code. IRS regulations accord greater credibility to records made at the time of travel or close to it, whilst a reconstruction carried out at the end of the year, based on memory and calendars, is much easier to challenge during an audit. A logbook completed on the same day, even in just a few words, is worth more than a perfectly drawn-up table compiled months later.
These rules apply to the US tax system, whilst other jurisdictions treat the mixed use of vehicles differently, with percentage limits on deductibility, their own requirements regarding logbooks, or special regimes for vehicles used exclusively for business purposes. In Romania, for example, the Tax Code generally limits the deductibility of vehicle expenses not used exclusively for business purposes to 50 per cent, and exclusive use must be proven, amongst other things, by means of logbooks. An entrepreneur working in another country should check the local rules with a qualified tax specialist in that country.
Vehicle costs, separated in the accounting system
A dedicated accounting system helps entrepreneurs understand transport expenses without mixing them up with household expenses. Recording vehicle costs in separate categories makes financial reports more useful and reduces the workload involved in preparing tax documents. Even those who are self-employed and work from home benefit from clear records of business transactions, and a separate bank account or card for the business, in turn, helps to organise financial matters.
Useful categories for transport expenses include:
- Fuel: petrol refuelling or electric charging required to operate the vehicle.
- Maintenance and repairs: servicing, spare parts and mechanical work.
- Insurance and registration: recurring costs associated with owning the vehicle.
- Parking and road tolls: amounts directly related to eligible business travel.
- Vehicle financing: interest on loans and lease records, kept separately for correct accounting treatment.
These categories allow expenses to be verified without having to repeatedly review transactions unrelated to them. However, separating payments remains an administrative task and does not prove that every transaction is deductible; therefore, owners must still determine the proportion of the vehicle’s shared expenses used for business purposes.
What economic sociology says about separating household and business finances
The advice to keep business funds separate from household funds has a longer history than any accounting software. Max Weber regarded the separation of the household from the enterprise as one of the conditions for the emergence of modern capitalism, alongside the rational accounting of capital. In the lectures published posthumously in 1923 under the title *Wirtschaftsgeschichte* and in his work *Wirtschaft und Gesellschaft*, Weber described the transition from a household in which family income and workshop capital formed a single pool of funds to an enterprise that calculates its profit separately, based on its own records. Without this separation, he argued, the entrepreneur cannot know whether his activity is generating a profit or merely consuming the family’s assets.
A car used for both purposes is an almost perfect example of the problem described by Weber, reappearing on the scale of a one-person business. The logbook, accounting categories and separate account are tools through which the entrepreneur reconstructs, each month, the boundary that large firms already have within their legal and accounting structure. The example in the article, with 60 per cent business use, illustrates precisely this calculation: a single asset, the car, is rationally divided between two different accounts. The same logic applies to cash reserves, and the analysis on building a cash reserve for small businesses without complicating their finances recommends, in the same vein, keeping savings separate from day-to-day working capital.
This separation also has a legal dimension that Weber could not have anticipated in its current form. In the United States, courts considering whether the owners of a limited liability company can be held personally liable for its debts take into account, amongst other factors, the commingling of personal and business funds. For a sole trader, where there is no legal separation between the owner and the business, separate accounts nevertheless remain the only way to demonstrate to the tax authorities which expenses relate to the business activity.
This framework has limitations that must be acknowledged. Weber’s thesis, like Werner Sombart’s related thesis on the role of double-entry bookkeeping, has been challenged by historians of accounting. Basil Yamey demonstrated in 1949, in the *Economic History Review*, that many merchants in the early modern period kept double-entry records without using them for investment decisions, which undermines the idea of a direct link between the records and economic rationality. Weber also worked with ideal types – theoretical constructs that simplify historical reality – and many family businesses still operate today with blurred boundaries between the household and the firm. The framework explains why this separation makes calculation possible, without guaranteeing that the entrepreneur will actually use the figures obtained.
Analysing transport costs for better profitability
Transport records can reveal operational costs that entrepreneurs overlook when assessing their profitability. A service provider who frequently travels long distances for short appointments may spend more than expected on fuel, vehicle wear and tear, and time spent behind the wheel. Analysing these costs per customer, per route or per project shows whether current prices accurately reflect the cost of services and supports better scheduling and more informed decisions.
For example, combining two nearby appointments into a single journey can reduce unnecessary distances and time spent behind the wheel. Companies that make frequent deliveries can, in turn, review their routes to find a more efficient schedule. Such adjustments boost operational efficiency without requiring major investments in new equipment or vehicles (major investments in new equipment or vehicles). Reliable expense records transform transport costs into information that business owners can use to assess their operations.
How to choose and verify a tax specialist
The recommendation to consult a qualified tax specialist, found in almost every guide of this kind, raises a practical question: how can an entrepreneur verify the qualifications of the person they choose? In the United States, anyone who prepares federal tax returns for a fee must hold a Preparer Tax Identification Number (PTIN); however, this number alone does not prove professional qualification. Only chartered accountants (CPAs), enrolled agents and solicitors have unlimited authority to represent clients before the IRS, including during audits and in appeal proceedings, whilst tax preparers without such qualifications may prepare tax returns but cannot represent their clients.
Verification can be carried out using public sources. The IRS maintains a searchable register of tax return preparers who hold accreditations and certain qualifications, listing each one’s name, town, state and postcode, whilst a certified public accountant’s licence can be verified in the database of the licensing board in the state where they practise. For an initial list of firms, the financial services category in the Jasmine Directory groups together firms in the sector, including a sub-category dedicated to accountancy, and the listings are reviewed by an editor prior to publication.
The limitations of such a listing must be made clear. It confirms that the firm exists, that it operates in the stated field and that it can be contacted; however, it does not certify the licence of each accountant, does not assess the quality of the advice provided, and does not constitute a tax recommendation. Checking the licence in the official register remains a mandatory step, and questions about experience with self-employed individuals who use their vehicle for both business and personal purposes will quickly reveal whether the specialist is familiar with the issues described in this article.
Several warning signs are described by the IRS itself. A tax preparer who refuses to sign the tax return or to include their PTIN on it, who calculates their fee as a percentage of the refund amount, or who asks for the refund to be paid into their own account is a serious cause for concern, as responsibility for the content of the tax return remains with the taxpayer, even when the errors are someone else’s fault. A reputable specialist, on the other hand, will ask for the mileage log and supporting documents, and enquiring about these at the first meeting is a good sign.
This separation also applies to the business’s public records
The boundary between personal and professional matters is not just about money. Many entrepreneurs who work from home use their home address as their business address, and this address then appears on online profiles, invoices and in business directories. For a business that visits clients rather than receiving them at its premises, most mapping platforms and directories allow a service area to be displayed instead of the exact address, whilst a dedicated business telephone number keeps client calls separate from personal ones. The same discipline that separates business mileage from personal mileage allows the entrepreneur to decide what information about themselves becomes public and to keep it consistent across all sources where the business appears.
Records must, in turn, be kept for a sufficient period of time. The IRS recommends, as a general rule, retaining supporting documents for at least three years after the filing of the tax return to which they relate, with longer retention periods in certain situations, such as when income is reported as significantly lower than the actual amount. For a depreciated vehicle, records of the purchase cost and the proportion of business use must be kept until the end of the tax year in which the car is sold or taken out of service.
A record-keeping routine that stands the test of time
Separating personal transport expenses from business ones works best when record-keeping becomes part of daily operations. Entrepreneurs should regularly update their logbook, keep supporting receipts and reconcile vehicle expenses with their accounting records. A quick monthly check helps to identify missing transactions before they become difficult to reconstruct and provides an opportunity to assess whether transport expenses remain in line with business needs.
The aim is to draw a clear distinction between personal use of the vehicle and legitimate business activity. Clear documentation supports accurate financial reporting, better-informed operational decisions and the correct preparation of tax returns. Whether an entrepreneur drives occasionally to meet clients or relies on a vehicle every working day, consistent record-keeping provides a clearer picture of transport costs, and this clarity protects both the business’s finances and the owner’s personal budget.
Thus, the seemingly technical issue of business mileage proves, on closer inspection, to be a small-scale version of the separation that Weber regarded as the foundation of modern economic calculation, recreated each month by the entrepreneur who uses the same vehicle for two different lives. It can be concluded that a logbook completed on the day of travel, separate accounts, a tax specialist verified in official registers, and public data kept consistently together form the boundary that a large firm has through its structure, whilst for a small business this boundary exists only to the extent that the owner maintains it. The information in this article is of a general nature and does not replace individual tax advice.
