I’ve watched the same story play out in a lot of companies: they launch a shiny new “global” per diem policy, then realize a few months later that no one can actually afford New York, London, or Tokyo without pulling out their own credit card.

If travelers are constantly subsidizing business trips, your per diem policy isn’t just tight. It’s not working.

This guide walks through how to design a global per diem strategy that’s tax-compliant, simple to manage, and realistic in high-cost cities. I’ll reference IRS, GSA, and State Department rules for context, but the approach works for international travel too—whether you’re budgeting for London, Singapore, or São Paulo.

1. Decide What You’re Optimizing For: Simplicity, Precision, or Fairness?

Before you open a spreadsheet or compare per diem vs actual expenses, ask a blunt question: Are we optimizing for admin simplicity, cost control, or traveler fairness? You can’t fully maximize all three at once.

  • If you optimize for simplicity, you’ll lean on flat or high–low per diem rates and accept that some cities will be slightly overfunded and others underfunded.
  • If you optimize for precision, you’ll use location-specific rates (GSA, State Dept, local benchmarks) and live with more complex rules.
  • If you optimize for fairness, you’ll probably blend both: simple where costs are predictable, precise where they’re not—especially in high-cost city travel.

In the U.S., you essentially have two ways to structure a domestic per diem policy:

  • Standard (location-specific) method – city-by-city rates via GSA.gov. For 2025, the standard CONUS rate is $178/day (about $110 lodging, $68 M&IE), but many cities are higher. See the GSA per diem lookup.
  • High–low method – just two IRS rates: $319/day for high-cost localities and $225/day for others, with embedded M&IE components (e.g., $86 vs $74) as described in IRS Notice 2024-68 and Notice 2025-54.

As a rule of thumb for a global per diem strategy:

  • Use high–low when your travel pattern is stable and mostly in similar markets (regional sales teams, recurring client cities, predictable routes).
  • Use location-specific rates when you’re constantly in new or extreme-cost markets (consulting, project work, construction, implementation teams).

If you skip this decision, you end up with a Frankenstein policy: part flat rate, part city-specific, part exception-based. No one understands it, and everyone works around it.

2. Stop Guessing: Anchor Your Rates to Real Benchmarks

Underfunding usually starts with a sentence like: Let’s just set meals at $50/day; that feels reasonable. Reasonable where? Boise or Boston? London or Lisbon?

Instead of guessing, anchor your international per diem rate calculation to three concrete benchmarks:

  1. U.S. federal per diem systems
    • GSA (CONUS) – city-specific lodging + M&IE for the continental U.S.
    • DoD (OCONUS) – Alaska, Hawaii, U.S. territories.
    • State Department – foreign per diem rates by city/country, a useful cost guide for global per diem decisions.
  2. IRS high–low rates

    For 2024–2026, the high–low per diem is $319 for high-cost and $225 for other U.S. localities, with M&IE components of roughly $86 and $74 respectively, per NYSSCPA’s summary.

  3. Local reality checks

    Pick a few representative cities in each region—say New York, London, Singapore, and São Paulo—and ask: Can a traveler get a safe hotel and three modest meals within this budget? If the answer is no, your per diem policy for high cost cities needs work.

From there, build a simple tiered structure for your per diem benchmarking for global travel:

  • Tier 1 – Global high-cost cities
    Think NYC, San Francisco, London, Zurich, Tokyo, Singapore. Peg these near the higher of GSA/State Dept rates or your own data. This is where business travel per diem underfunding hurts the most.
  • Tier 2 – Standard cities
    Peg these around the U.S. standard rate (e.g., $178/day equivalent), adjusted for region and typical hotel class.
  • Tier 3 – Low-cost cities
    You can go lower here, but still sanity-check with real prices. Don’t assume “emerging market” means “cheap.”

If you’re using the IRS high–low method in the U.S., you can map your global tiers to those two buckets domestically and to State Dept tiers abroad. The important part: document how a city gets assigned to a tier and commit to updating international per diem rates at least annually when IRS/GSA/State Dept rates change.

IRS Per Diem Rates for 2025: What Changed

3. Separate Lodging, Meals, and Incidentals – Or You’ll Misprice Everything

One of the fastest ways to underfund high-cost cities is to treat per diem as a single blob and forget that lodging and meals behave very differently across markets.

In many cities, hotel prices swing wildly by season and weekday, while meal costs stay relatively stable. In others, lodging is cheap but eating out is pricey. If you don’t separate these, you’ll either:

  • Overpay in low-lodging markets, or
  • Underpay in high-lodging markets and push people into unsafe or impractical hotels.

Here’s a clean way to structure your high cost city travel budget and avoid common corporate per diem policy mistakes:

  • Option A: Full per diem (lodging + M&IE)

    Use this when employees book their own hotels. For U.S. high–low, that’s the $319 / $225 combined rate. Spell it out in your policy: This amount is intended to cover both hotel and daily meals/incidentals. When you later compare per diem vs reimbursement or actual expenses, you’ll know what you were aiming to cover.

  • Option B: M&IE-only per diem

    Use this when the company books and pays lodging directly. In the U.S., the IRS allows M&IE-only rates (e.g., $86 for high-cost, $74 for other localities under the high–low method). This is often the cleanest way to avoid underfunding in expensive hotel markets: you control the hotel cost and give a realistic meal budget.

  • Option C: Incidental-only per diem

    There’s still a $5/day incidental-only rate for tips and similar costs, per Thomson Reuters and Eide Bailly. Use this when meals are fully catered or included in conference fees.

Globally, mirror this structure in your global per diem strategy:

  • Set separate internal caps for lodging and M&IE by tier.
  • Decide when you’ll book hotels centrally vs. let employees choose.
  • Make it explicit in your policy which component the per diem covers on each trip.

When you don’t separate these, travelers end up choosing between a safe hotel and dinner. That’s not a decision you want them making on your behalf.

4. Build a High-Cost City Playbook, Not Just a List

Most companies eventually realize they need a high-cost city list. Fewer realize they also need a playbook for how those cities are handled.

The IRS already maintains a list of high-cost localities for the high–low method, and it changes annually. Cities like Los Angeles have been added; others like Oakland have been removed or have seasonal high-cost periods. That’s useful, but it’s only a starting point for a fair per diem for business travelers.

Here’s what I’d include in a high-cost city playbook:

  • Clear criteria

    For U.S. trips, you can piggyback on IRS rules: high-cost localities are those with a federal per diem of at least a certain threshold (e.g., $272+). For international travel, use State Dept rates or your own cost-of-living index to decide which cities land in your top tier.

  • Seasonality rules

    Some cities are high-cost only during certain months (resort areas, major events, peak tourist seasons). Decide whether you’ll mirror the IRS seasonality or simplify to always high-cost for internal purposes. Simpler rules are easier to explain and enforce.

  • Automatic upgrades

    In designated high-cost cities, you might automatically:

    • Use the high-cost per diem tier.
    • Require company-booked lodging to avoid unsafe neighborhoods.
    • Allow exceptions for last-minute price spikes with manager approval.
  • Communication templates

    Pre-written language in travel approvals, for example: This trip is to a high-cost city; your per diem will be X for lodging and Y for meals. No surprises.

The goal is simple: when someone books a trip to an expensive destination, no one should be surprised by the per diem. Not the traveler, not the manager, not payroll.

5. Decide How Much Risk You’ll Take on Tax Compliance

Per diem is attractive because it can be non-taxable and low-friction when done right. Done wrong, it turns into taxable wages, creates audit risk, and frustrates everyone.

Here are the key U.S. rules to design around (and mirror conceptually in other countries when you build your global cost guide for per diem):

  • Accountable plan basics

    To keep per diem non-taxable, you need an accountable plan: business connection, substantiation, and return of excess. Employees don’t need receipts for every meal, but they must document date, place, and business purpose of each trip, as emphasized in multiple IRS summaries and firm write-ups.

  • Stay within IRS rates

    If your per diem does not exceed the applicable IRS rate, it’s deemed substantiated. Any unspent portion is not taxable and doesn’t need to be returned. If you pay more than the IRS rate, the excess must be either:

    • Taxed as wages, or
    • Substantiated with actual receipts, or
    • Returned by the employee.
  • Consistency rules

    Once you use the high–low method for an employee’s U.S. travel in a year, you must use it consistently for all their CONUS trips that year, and you can’t change the method in the last three months. You can still use other methods for OCONUS travel.

  • Owner limitations

    Owners with 10%+ interest generally can’t use the high–low per diem method. They may need actual expenses or different per diem rules.

So you have a choice:

  • Stay at or below IRS/GSA/State Dept rates and keep everything clean and non-taxable.
  • Intentionally exceed them in certain high-cost markets, but treat the excess as taxable wages or require receipts for the difference.

Be honest about it. If you’re going to be generous in places like London, New York, or Singapore, say so: We pay above IRS per diem in these cities; the excess will be taxed as income. That’s far better than a policy that quietly breaks the rules.

6. Protect Travelers from Underfunding Without Blowing Up Your Budget

Even with solid benchmarks, edge cases will show up: conferences that spike hotel prices, last-minute bookings, or cities that have become more expensive since you last updated your tiers.

Instead of pretending your per diem is perfect, build in controlled flexibility so you can adjust without turning every trip into a negotiation.

  • Exception triggers

    Define when a traveler can request more than the standard per diem. For example:

    • When the lowest safe hotel within X miles of the worksite exceeds your lodging cap by more than Y%.
    • When a major event (trade show, festival, global conference) drives prices above normal ranges.
  • Evidence requirements

    Ask for simple proof, not a novel: screenshots of typical hotel prices, conference hotel rates, or a short note from the travel team.

  • Pre-approval workflow

    Route exceptions through managers and finance, with clear SLAs. If you make this painful, people will either eat the cost or game the system.

  • Post-trip review

    When you see repeated exceptions in the same city, that’s a signal: your base per diem is wrong. Update the tier instead of approving one-offs forever.

The aim is to avoid two extremes:

  • Take it or leave it per diems that quietly punish travelers in expensive destinations.
  • Unlimited exceptions that turn your policy into a constant back-and-forth.

7. Make the Rules Obvious: What Employees Actually Need to Know

Most frustration with per diem isn’t about the exact dollar amount. It’s about surprises. People find out after the trip that they were over the limit, or that unused funds must be returned, or that they logged the business purpose incorrectly.

Every traveler should be able to answer these questions before they book:

  • What is my daily per diem for this trip?

    Spell out lodging vs. meals vs. incidentals. If lodging is company-paid, say so clearly. This is especially important in high-cost cities where the per diem vs reimbursement conversation can get tense.

  • What’s covered and what’s not?

    Use a simple list: meals, non-alcoholic drinks, tips, local transport to meals, etc. Exclude personal upgrades, minibar, companion travel, and so on, as many policy templates (like MangoApps’ travel policy framework) recommend.

  • Do I keep unused per diem?

    Some companies let employees keep the difference if they spend less; others require return of excess. Either approach can work; ambiguity does not.

  • What documentation do I need?

    Even with per diem, employees must record date, location, and business purpose. Make this easy with your expense tool or a simple form.

  • When will I be reimbursed?

    Set clear timelines for submitting claims and for payment. This supports accountable plan treatment and, in some jurisdictions, wage law compliance.

Put this in a short, human-readable policy, not just a dense legal PDF. And train managers: they’re the ones who will get the late-night messages when someone can’t afford dinner in a high-cost city.

8. Use Tools to Reduce Friction, Not to Hide a Bad Policy

Software won’t fix an unfair per diem strategy. But it can make a good one much easier to run at scale.

Modern travel and expense tools can help you manage a global per diem strategy without drowning in spreadsheets:

  • Auto-apply the right per diem rate based on city and dates (using GSA/State Dept data and your own tiers).
  • Handle M&IE-only vs. full per diem depending on who books lodging.
  • Centralize hotel folios and incidentals so employees don’t front large amounts on personal cards.
  • Flag trips where actual hotel prices are consistently above your lodging cap – a clear signal to revisit your tiers for cities like London, New York, or Singapore.

But tools are just the plumbing. The real questions behind a fair per diem for business travelers are still yours to answer:

  • Are your rates anchored to reality, not wishful thinking?
  • Do you treat high-cost cities differently on purpose, not by accident?
  • Are you honest about tax treatment when you exceed official per diem rates?
  • Do travelers know the rules before they travel, not after the expense report?

If you can say yes to those, you’re already ahead of most organizations. And your people won’t have to choose between doing their job and paying out of pocket in the world’s most expensive cities.