What is a tax deduction?

Published Monday 19 October 2026

Table of contents

• Tax deductions definition
• Example of a tax deduction calculation
• Types of tax deductions for small business
• What you can't claim as a tax deduction
• How to claim tax deductions
• Record keeping requirements
• Common tax deduction mistakes to avoid
• Simplify your tax deductions with Xero
• FAQs on tax deductions
• Related terms
• Learn more about tax deductions

Key takeaways

• A tax deduction is a business expense that reduces your taxable income, meaning you pay less tax overall. Common deductible expenses include office costs, business travel, professional services and marketing.
• Keep detailed records of business expenses, including receipts, invoices and proof of business purpose. Retention periods vary by country, for example generally 3 years in the US and at least 5 years in the UK.
• If an expense is used for both personal and business purposes, you can only claim the business portion. As an illustrative example, if you use your phone 80% for work, you can deduct 80% of the cost.
• Using accounting software to capture and categorise expenses as they happen makes it easier to track every eligible deduction and simplifies tax time.

Tax deductions definition

A tax deduction is a business expense that reduces your taxable income, so you pay less income tax. Tax deductions work by subtracting eligible expenses from your gross income to arrive at your taxable income.

The Organisation for Economic Co-operation and Development (OECD) treats deductions as amounts taken off the tax base: the income your tax is calculated on.

Common deductible expenses for small businesses fall into a few groups:

• Office expenses: rent, utilities, equipment and supplies
• Business travel: flights, car hire, accommodation and meals
• Professional services and insurance: legal and accounting fees, plus business insurance
• Marketing costs: advertising and website expenses

As a general observation, deduction rules and rates differ from one country to the next, as do the terms used for them. Each country's tax authority sets the rules for which expenses you can claim and when. Examples include the Internal Revenue Service (IRS) in the United States and HM Revenue and Customs (HMRC) in the UK.

Your accounting method can also affect timing; under cash accounting, you generally record an expense when you pay it. Always check your tax authority's website for the latest guidance on eligible deductions.

Getting the numbers right starts with understanding how deductions affect your tax. The next section walks through an illustrative example.

Example of a tax deduction calculation

Tax deductions reduce your taxable income by subtracting legitimate business expenses from your total income. Here's an illustrative example in US dollars (USD) showing how it works in practice.

Jo owns a photographic studio and earned $77,000 last year. She has $15,000 in deductible business expenses, which reduces her taxable income to $62,000.

$77,000 (gross income) − $15,000 (deductions) = $62,000 (taxable income)

Jo pays tax on $62,000 instead of her full $77,000 income, so her tax bill is lower. How much she saves depends on her tax rate.

Business purpose requirement

For an expense to qualify as a tax deduction, it must have a legitimate business purpose. A camera is deductible for a photographer, but not for a baker.

Each country sets its own test for business purpose. In the United States, for example, IRS Publication 334 says a business expense must be ordinary and necessary. That means it's common in your industry and helpful for your business.

Personal vs business expenses

Only the business share of an expense is deductible, so you need to separate personal and business costs.

• Personal expenses: generally not deductible, for example groceries and personal clothing
• Mixed-use expenses: claim only the business portion of the cost
• Purely business expenses: fully deductible when used exclusively for work

Record keeping essentials

Keep receipts for all expenses you plan to deduct. Proper documentation protects you during a tax audit and helps you claim every legitimate deduction.

Now that you understand how deductions are calculated, here are the specific types of expenses you can claim.

Types of tax deductions for small business

Small businesses can claim a range of deductions, but what qualifies and how much you can claim depends on where you're based. Check the latest guidance from your tax authority or speak with a tax professional to make sure you claim the right expenses.

Work-related expenses

These are costs you incur to earn your income. They can include vehicle and travel expenses, training related to your work, and uniforms or protective clothing. Clothing deductions are usually available only in limited circumstances, so check what your tax authority allows.

Business operating costs

These are the day-to-day running costs of your business. They include items like rent for your office, staff salaries and office supplies. Some countries also let eligible small businesses deduct the full cost of certain assets straight away, which the depreciation section below covers.

Home office deductions

If you work from home, you may be able to claim a portion of your household running expenses. Many tax authorities offer a simplified method alongside calculating your actual costs.

In the United States, the IRS simplified option lets you deduct $5 per square foot of home used for business, up to 300 square feet. The space must be used regularly and exclusively for business.

In the UK, sole traders working from home 25+ hours a month can use flat rates of £10–£26 a month, based on hours. Both simplified methods are optional, and calculating actual costs may give a higher deduction if your expenses are significant.

Vehicle and travel expenses

If you use your vehicle for business purposes, you can usually claim the cost of those trips. Many tax authorities offer two ways to calculate car expense deductions:

• Standard mileage rate: claim a set rate per business mile instead of your actual costs
• Actual cost method: claim the business-use percentage of your actual running costs, backed by a mileage log

In the United States, the 2026 IRS business mileage rate is 72.5¢ per mile for January–June and 76¢ for July–December.

In the UK, from 6 April 2026, self-employed people can claim 55p a mile for the first 10,000 business miles by car, then 25p. Rates change, so check your tax authority before you claim.

Business travel expenses like flights and accommodation for work trips are also usually deductible, as long as the main purpose of the trip is business.

Self-education expenses

Many tax authorities let you claim self-education expenses if the course or training directly relates to your current work. Typically, the education must maintain or improve a skill or knowledge your current role requires.

Eligible costs can include course fees and textbooks. Training for a new job or a different occupation is often excluded, so check your local rules.

Depreciation and asset write-offs

When you buy assets for your business, such as equipment, tools or vehicles, these capital expenses are usually claimed over time through depreciation. In accounting, International Accounting Standard 16 (IAS 16) describes depreciation as spreading the depreciable amount of an asset's cost systematically over its useful life.

Tax depreciation rules are separate and vary by country, and some let small businesses write off eligible assets faster. In the United States, for example, the Section 179 deduction lets you deduct part of an eligible asset's cost in its first year of use.

Check your tax authority for current limits and eligibility, as these can change each tax year.

Knowing what you can claim is only half the picture. It's equally useful to understand what you can't deduct.

What you can't claim as a tax deduction

Some expenses are generally not deductible, however closely they seem connected to your business. Being clear on what falls outside the rules helps you avoid penalties and wasted effort at tax time.

Common examples include the following.

• Personal expenses: groceries, personal clothing, gym memberships and other costs unrelated to earning your income
• Fines and penalties: traffic fines, parking tickets and penalties from tax authorities, even if you incurred them during work
• Entertainment: the cost of entertaining clients or staff at restaurants, sporting events or social functions
• Capital expenses: costs of buying or improving a long-term asset, which you may claim through depreciation over time instead
• Private portion of mixed expenses: the personal share of a cost that's partly for business

In the United States, fines paid to a government agency for breaking the law are usually not deductible, according to IRS Publication 334. US rules generally exclude entertainment too.

US business meals are treated differently. IRS Publication 463 lets you generally deduct 50% of the cost if you or an employee attend and it isn't lavish.

Treatment varies by country. If you're unsure whether a specific expense qualifies, check your tax authority's guidance or speak with a tax professional.

Once you know which expenses qualify, the next step is understanding how to claim them correctly.

How to claim tax deductions

Claiming deductions can be simple. It comes down to following a clear process and keeping good records throughout the year.

Follow these steps to claim your deductions:

1. Confirm you spent the money yourself and weren't reimbursed.
2. Make sure the expense directly relates to earning your income.
3. Keep a record (like a receipt) to prove the expense.
4. Calculate the deductible amount, separating any personal use.
5. Enter each deduction in your tax return under the correct category before you file.

Using accounting software to track deductions

Tracking expenses manually can lead to missed deductions and errors. Using accounting software helps you capture and categorise expenses as they happen, so you can claim all your eligible deductions at tax time.

Good records are the foundation of every successful deduction claim. Here's what tax authorities typically expect you to keep.

Record keeping requirements

Tax authorities generally require you to keep records that prove your income and expenses. Good records make tax time smoother and protect you in case of an audit.

What records to maintain

You should keep records for all your business transactions. This includes invoices, receipts, bank statements and contracts.

For expenses, your records should show:

• what you bought
• when and where you bought it
• how much you paid
• how it relates to your business

How long to keep records

Retention periods vary by country, and the clock can start at different points. Here are some examples to compare with your local rules.

In the United States, the IRS generally asks you to keep records for 3 years after filing, though some situations require 6 or 7 years.

In the UK, sole traders and partners must keep records for at least 5 years after the 31 January deadline for the relevant tax year.

In Canada, the Canada Revenue Agency (CRA) generally asks you to keep records for 6 years after the relevant tax year ends. Whatever your location, keep your filing system organised and accessible.

Digital vs physical records

You can usually keep records in paper or digital format. Digital records are easier to store, search and back up. Use software to snap photos of receipts and reduce paper clutter.

Even with the right records in place, there are common pitfalls that can trip you up. Here's what to watch out for.

Common tax deduction mistakes to avoid

Knowing about common mistakes can help you claim with confidence at tax time.

Personal vs business expense confusion

You can only claim the business-use portion of an expense. If you use your car for both business and private trips, you need to separate the costs and only claim the business part.

Insufficient documentation

A deduction needs a record to back it up. Keep clear, organised records for every claim, and store them securely for as long as your local retention period requires.

Overclaiming risks

If you claim something you're not entitled to, you may face penalties from your tax authority and have to repay the tax you saved. If you're unsure whether an expense is deductible, check your tax authority's guidance or ask an accountant or bookkeeper.

Staying on top of your deductions throughout the year is easier with the right tools. Here's how Xero can help.

Simplify your tax deductions with Xero

Tracking every receipt and categorising every expense throughout the year can feel like a big job. Xero accounting software automates the process by connecting to your bank feeds, matching transactions and organising your expenses in real time.

With Xero, you can snap photos of receipts, categorise expenses as they happen and generate reports that make tax time straightforward. Your accountant or bookkeeper can access your data directly, so there's less back-and-forth at tax time.

Preparing all year means you claim every deduction you're entitled to. Get one month free and start tracking your deductions with Xero.

FAQs on tax deductions

Here are answers to some frequently asked questions about tax deductions.

Can you claim a tax deduction without receipts?

Most tax authorities expect proof for every claim, and the rules vary by country. In the US, IRS Publication 463 waives receipts for travel, gift and transport expenses under $75 (except lodging), but you must still record the details.

What's the difference between a tax deduction and a tax credit?

A tax deduction reduces the income you're taxed on, while a tax credit comes straight off the tax you owe. In an IRS tutorial example, a $200 deduction at a 15% tax rate saves $30, while a $200 credit saves the full $200.

Can I claim personal expenses as business deductions?

You can only claim the business portion of an expense. If an expense is partly personal, you need to calculate and claim only the percentage used for business purposes.

Is insurance tax deductible if you're self-employed?

In the US, IRS guidance says sole proprietors may be able to deduct health insurance premiums, including long-term care cover, for their family. Premiums for policies that replace lost earnings due to sickness or disability aren't deductible in the US.

Are retirement contributions tax deductible?

In the US, IRS rules let sole proprietors deduct their own contributions to retirement plans, such as a Simplified Employee Pension (SEP) plan. Contribution limits apply and other countries have their own rules, so check with your tax authority.

How do I know if an expense is tax deductible?

An expense is generally deductible if it directly relates to earning your income and you have a record to prove it. Your tax authority publishes guidance for different industries, and a tax professional can give you advice specific to your situation.

Related terms

• Expense
• Income tax
• Opex vs capex
• Cash accounting
• Audit

Learn more about tax deductions

• How to prepare tax returns
• How to do payroll
• Business accounting
• Claim expenses with Xero