What is per diem? It’s a term you’ll encounter in companies, government bodies and organisations that move people on business. In its simplest sense, a per diems is a daily allowance designed to cover travel-related expenses such as meals and incidental costs while you’re away from home on work. But the reality is more nuanced: different employers, sectors and jurisdictions use per diem in slightly different ways, with varying rules about receipts, tax treatment and how rates are set. This article unpacks the concept, explains how per diem works in practice, and offers practical guidance for individuals and organisations looking to implement a fair, compliant and effective per diem policy.
What Is Per Diem? A Clear Definition
Per diem, literally Latin for “for a day,” functions as a daily allowance provided to employees or contractors to cover costs incurred while travelling on business. The core idea is simple: you receive a fixed sum each day of travel to cover meals, incidental expenses (such as tips, toiletries, transit fees, and other small costs) and sometimes local transportation. The important distinction is that per diem typically covers day-to-day expenses without requiring you to submit individual receipts for every item. Depending on policy, it may also include a component for incidentals beyond meals, or it may be strictly meals and incidental expenses.
In short, what is per diem? It is a structure to streamline reimbursement, reduce admin overhead, and provide travellers with predictable spending limits. It differs from reimbursing exact receipts because it relies on flat rates or location-based allowances rather than every purchase being itemised.
Origins and Context: Why Per Diem Exists
The concept of per diem emerged to simplify travel reimbursements in organisations that routinely send staff on business trips. Before per diem, employees often had to submit detailed receipts for meals and incidental expenses, which created administrative work and potential delays. Per diem arrangements emerged as a practical solution to speed reimbursements and reduce friction for travellers and finance teams alike. Over time, the approach has evolved, with many organisations adopting location-based rates to reflect regional price differences and cost of living. In some sectors, the per diems are defined by industry guidelines or government standards, while private companies may set their own scales, tied to budgets and policy objectives.
How Per Diem Works: Rates, Calculations and Policy Design
Where the Rates Come From
Rates are usually determined by the organisation’s policy. Some employers use fixed rates for all travel, while others differentiate by destination—domestic postings may have lower rates than international trips, and major cities often command higher daily allowances due to higher costs. In many organisations, official guidance or industry benchmarks inform the rate-setting process. When per diem is used by government contractors or public sector bodies, rates may align with specific statutory or contractual guidelines to ensure consistency and fairness across programmes.
Domestic vs International: Different Rates
Domestic per diem rates tend to reflect the average cost of meals and incidental expenses within the country or region of travel. International travel introduces more complexity: rates differ by country, city, and sometimes even locality. High-cost destinations, such as large capitals, often have higher per diems to maintain the traveller’s standard of living while away, whereas lower-cost locations may justify smaller allowances. It’s common for organisations to provide a base international rate with adjustments for major cities or regions, acknowledging that expenses vary widely by place.
What Is Per Diem? How It Is Calculated
The calculation typically involves multiplying the daily rate by the number of days on business travel. Some policies also specify partial-day rates for travel that begins or ends part-way through a day. In addition, policies may cap the total per diem for the entire trip or impose a ceiling by employee role or project. For example, you might be offered a base per diem of £40 per day for domestic travel and £75 per day for international travel in major cities, with adjustments for shorter trips or weekend extensions. It’s important to understand the policy’s rules on partial days, weekends, and the handling of days spent in more than one location during a single trip.
What Is Per Diem? Location-Based Versus Flat-Rate Models
Some organisations adopt location-based rates that reflect the local cost of meals and incidental expenses. Others use flat-rate per diems regardless of destination. Location-based models can be more equitable, as they are more closely aligned with real-world costs; flat-rate models are simpler to administer, particularly for frequent travellers or multi-destination trips. A hybrid approach is also common, where a base rate applies to all travel, with adjustments for particularly expensive destinations.
Per Diem Vs Other Travel Allowances: Key Differences
Subsistence vs Incidental Expenses
Often, per diems are framed to cover two broad categories: meals and incidental expenses. Some policies separate these allowances, specifying a meals-only per diem, a separate incidental expense cap, or a combined rate. Understanding what is included under the per diem helps travellers plan meals and discretionary spending without breaching policy.
Reimbursement vs Allowance: Tax Implications
Per diem can be treated as a reimbursement, a non-taxable allowance, or as part of salary, depending on how the policy is designed and the jurisdiction. In the UK, tax treatment hinges on whether the per diem is fully optional, whether it requires receipts, and whether it aligns with HMRC guidance on travel expenses. A well-designed per diem policy can minimise administrative effort while preserving tax efficiency for both the employee and employer.
Per Diem vs Actual Expenses
With per diem, you don’t need to submit every receipt. When actual expenses are reimbursed, you must present receipts for meals, incidentals and other costs. While actual expense reimbursement can be more precise, it also creates more paperwork and potential disputes over what qualifies. Per diem offers predictability and simplicity, but it also requires trust that travel costs won’t exceed the allocated funds.
Per Diem in the UK and Abroad: Rules, Tax and Compliance
UK Guidelines and HMRC Considerations
The UK does not prescribe a universal, one-size-fits-all “per diem” rate across all employers. Instead, organisations typically design policies that reflect local context, costs and regulatory expectations. In practice, some employers use HMRC-approved daily allowance concepts to determine tax treatment. If a per diem is structured as a genuine, regular allowance and the traveller does not have to supply receipts, part of the payment could be tax-free up to the policy’s limits, subject to compliance with statutory requirements. It’s crucial for both employers and employees to document the policy clearly, establish the rate structure, and ensure consistency with employment contracts and payroll practices.
International Travel: Considerations for UK Travellers
When travelling internationally, exchange rates, varying meal costs and cultural norms affect what is reasonable to claim. A well-designed per diem policy will specify how to handle currency conversion, time zone differences and partial-day allowances for international trips. In some cases, international per diems will be higher to accommodate dinners with clients or meals in destinations with higher living costs, while still maintaining fairness and accountability.
Who Benefits From Per Diem?
Employees and Business Travellers
For staff and contractors, per diem provides financial predictability, simplifies expense submission and reduces out-of-pocket spending while on assignment. It can also support morale by reducing the stress of budgeting on the road and avoiding the anxiety of counting every penny spent. The key is clarity: travellers should know what is included, what is excluded, and how to handle any expenses that fall outside the policy.
Employers: Budget Control and Compliance
From the organisation’s perspective, per diem reduces administrative overhead, helps with cash flow management, and standardises travel costs across teams and locations. A clear per diem policy supports internal controls, audit readiness and consistency with corporate governance. It also minimises the risk of expense disputes with employees, provided the policy is transparent and consistently applied.
Common Pitfalls and How to Avoid Them
Receipts, Caps, and Documentation
One of the most common issues is misunderstanding what needs to be documented. If the policy allows a per diem, receipts may not be required for covered items, but there should still be a mechanism to show the trip’s dates, destinations, and total allowances claimed. If a traveller spends more than the per diem, the excess should be charged to the employee or reimbursed under a separate policy, depending on the organisation’s rules.
Income Tax and National Insurance Issues
Tax and social security treatment can become complex, especially for multi-country assignments or long-term secondments. It is essential to align per diem policy with payroll processes, ensure correct tax treatment, and maintain documentation for potential audits. In some circumstances, per diem may be treated as part of the salary package rather than a separate expense, altering tax and NI outcomes for the employee.
How To Claim Per Diem: A Practical Step-by-Step Guide
Before the Trip: Policy Review
Understand the policy: what the daily rate covers, what constitutes an eligible trip, how to handle partial days, and what documentation is required for exceptions. Clarify whether the per diem includes international travel and how currency conversions are managed.
During the Trip: Keeping Track
Maintain a travel log with trip dates, destinations, purpose, and any deviations from plan. If you are using a flat per diem, you’ll simply track days away and dates on which the allowance applies, rather than collecting every receipt.
After the Trip: Submitting Claims
Submit claim forms promptly, attaching any required documentation and confirming that the per diem was used in accordance with policy. If you incurred expenses above the per diem, detail the excess and the approved method for reimbursement according to policy.
Practical Examples: What Per Diem Looks Like in Real Life
Scenario A: Domestic Travel for a Conference
A UK-based consultant travels to Manchester for a two-day conference. The per diem rate for domestic travel is £40 per day. The consultant spends meals, coffee and tips that total £70 over two days. They submit the claim with the two travel days, and any excess above the per diem (£70 – £80) is not a concern since the total is within the two-day allowance. If the policy requires receipts for any amount above the per diem, there would be a separate process for those expenses. This simple domestic example illustrates how per diem can streamline reimbursement while remaining within policy limits.
Scenario B: International Client Visit
An employee travels to Paris for a week to meet clients. The policy provides £75 per day for international destinations in major European capitals. The traveller completes the trip, using the per diem for meals and incidental expenses. In this case, the per diem covers most daily costs, with a predictable budgeting outcome for the trip. If the policy states that certain meals with clients must be supported by receipts, or if there is a cap on entertainment expenses, those rules will apply for that portion of the trip.
What Is Per Diem? The Future of Daily Allowances
Automation and Digitalisation
As organisations move towards digital expense platforms, per diem processes are becoming more automated. Rates can be uploaded to payroll systems, travel booking tools can pre-approve allowances based on location, and real-time dashboards can monitor spend against budgets. This reduces manual data entry, cuts processing times, and improves visibility for finance teams and travellers alike.
Policy Alignment with Cost of Living
Forward-looking organisations may adjust per diem rates in response to inflation, cost of living changes or macroeconomic conditions. A dynamic policy that revises rates cautiously can help ensure that travellers maintain their standard of living during trips while keeping cost control intact for the organisation.
What Is Per Diem? Key Takeaways
- Per diem is a daily allowance to cover meals and incidental expenses while travelling on business.
- Rates can be fixed, location-based or a combination, and may differ for domestic versus international travel.
- Per diem can simplify administration, but it requires clear policy, consistency and awareness of tax implications.
- UK practices vary; some organisations align with HMRC guidance for tax treatment, while others set their own internal rules.
- Proper documentation, clear communication, and timely submission are essential for a smooth per diem process.
What is per diem? It is a practical toolkit for managing travel costs. When adopted thoughtfully, it protects travellers from out-of-pocket expenses, helps employers plan budgets with greater certainty, and reduces the administrative burden that used to accompany expense reporting. By understanding the fundamentals—rates, coverage, eligibility, and compliance—both sides can benefit from a policy that is fair, transparent and efficient.
Glossary: Quick Definitions You Might Find Useful
- Per Diem
- A daily allowance provided to cover meals and incidental expenses while travelling for work.
- Incidental Expenses
- Small, day-to-day costs incurred away from home, such as tips, internet access, transit fares, and toiletries.
- Subsistence Allowance
- A synonym for per diem in some organisations, emphasising meals and essential spending while travelling.
- Receipts
- documentary proof of purchases. Policies vary on whether receipts are required when using the per diem.
- Tax Treatment
- How per diem payments are treated for tax and National Insurance purposes, depending on policy structure and jurisdiction.
In summary, what is per diem? It is a versatile tool for managing travel expenses efficiently, with the potential to save time, improve policy compliance and support fair compensation for staff on the road. Whether you are an employee negotiating a new role, an employer refining a travel policy, or a finance professional aiming to streamline submissions, a well-structured per diem framework can deliver tangible benefits while keeping costs predictable and transparent.