Business Central Expense Agent Adds Date- and Vehicle-Based Mileage Rates in 2026

The timing makes sense. In 2026 the IRS changed its business mileage rate halfway through the year, so a single "standard rate" field was no longer enough for U.S. companies that follow the IRS figure.

What Microsoft announced​

The Microsoft 365 / AI at Work roadmap entry, titled "Expense Agent – Add date ranges and vehicle types in your mileage calculation," describes these additions to the Mileage Rate Setup page:

• Date-bounded rates. A rate can be valid only within a set date range, so organizations can handle rate changes over time.
• Rates by vehicle type. Different reimbursement rates can be set for different vehicle categories. Microsoft's examples are cars, motorcycles, electric vehicles and categories the organization defines itself.
• Automatic selection. When someone creates a mileage expense, the Expense Agent checks the trip date and the selected vehicle type, then applies the matching rate.
• Policy changes without rework. Microsoft says organizations can follow changing regulations, company policies and regional standards without manually recalculating submitted mileage claims.

The roadmap metadata:

Microsoft's roadmap page says its dates are estimates and that all information is subject to change. With the status still "In development," treat October as a target, not a launch date.

The feature also appears in Microsoft Learn's "What's new" page for Business Central 2026 release wave 2 (update 29.0) public preview. It is listed under Expense Agent as "Add date range and different vehicle types in your mileage calculation in Expense Agent," next to other Expense Agent items:

• interim approvers
• automatic withholding tax calculation
• AI-based approval validation
• better duplicate prevention
• travel requisitions

Section summary: a single flat mileage rate becomes a table of rates, each tied to a date range and a vehicle type, and the agent picks the right one for each trip.

Why the date-range part matters this year​

This is more than a theoretical feature. According to the IRS's standard mileage rates page, the business rate is 76 cents/mile for July 1 – Dec. 31, 2026, versus 72.5 cents for Jan. 1 – June 30. Tax-practice coverage notes that the IRS typically sets standard mileage rates once a year in the fall, and that rising fuel prices pushed this year's off-cycle change.

The rate is tied to when the driving happened. As one reimbursement guide explains, which rate you use depends on the date you drove, not the date you file or get paid.

Picture an employee who submits a late-June trip in mid-July. With one global rate field, an administrator who updated the rate on July 1 would pay that trip at the new rate unless someone caught it. Date-ranged rate records are meant to handle exactly this case: the June trip gets the June rate and the July trip gets the July rate.

Being able to store several effective-dated rates is the core of the feature.

Vehicle types: useful, but check your own policy​

The vehicle-type part needs some care. At least for U.S. federal standard rates, one tax-advisory summary notes that the IRS figures apply uniformly to all vehicle types, including gasoline, diesel, electric, and hybrid models.

So separate rates for EVs or motorcycles will mostly come from:

• internal company policy, such as paying more for vans that carry equipment
• other countries' reimbursement schemes
• regional rules

Microsoft's roadmap text mentions "regional reimbursement standards," which points at multinational tenants. But the feature makes rates configurable. It does not check whether a rate is legal. Business Central will apply the rates you enter; whether they meet tax rules is still finance's job.

How mileage works in Expense Agent today​

Here is the current setup the feature builds on. According to Microsoft Learn's prerelease page "Set up per diem and mileage allowances" (labeled a production-ready preview), mileage is configured like this:

1. Open Search (Alt+Q), enter Expense Agent Setup, and choose the related link.
2. On the Allowance FastTab, set Standard Rate of Mileage to the reimbursement rate per distance unit.
3. In Default Mileage UOM, choose the unit, such as miles or kilometers.

On the user side, the same documentation describes these steps:

• Pick a mileage category.
• Enter starting and ending points as route descriptions.
• Enter the distance in the Mileage field.
• Optionally select Round Trip, which doubles the amount.

The Amount field is then calculated automatically.

Microsoft's Expense Agent overview also says the app calculates the distance and reimbursement amount based on your company's mileage rate. That phrase points to one company rate, and that is the limit the new feature removes.

There is already an effective-dating precedent in the same product. Per diem rules in Expense Management Rules have an optional Effective Date field. The mileage change brings that kind of time awareness to mileage.

Section summary: today you get one standard mileage rate and one unit of measure. The update adds a dated, vehicle-aware rate table on top.

What Microsoft hasn't documented yet​

Some details have not been published, and anyone who has run an ERP rollout will want answers before go-live:

• Exact field names on the new Mileage Rate Setup page, and whether it replaces or sits alongside Standard Rate of Mileage.
• How vehicle types are created and how users pick one on a mileage line.
• Overlapping date ranges. It's not clear what happens if two records cover the same day for the same vehicle type.
• Gaps. It's not clear what the agent does when no rate matches, for example a trip dated before your first record, or a claim with no vehicle type.
• Already-calculated lines. Microsoft says you won't need to manually recalculate submitted claims, but it hasn't said whether existing expense reports are ever recalculated or whether users can override the applied rate.
• Availability beyond the Worldwide (Standard Multi-Tenant) listing, including any regional or licensing limits.

Until Microsoft documents these, don't assume any particular behavior.

How to prepare for testing​

These steps are my own advice based on how the feature is described, not Microsoft's setup requirements.

1. Use a sandbox. Microsoft's 29.0 preview applies only to Business Central online sandbox environments, not production or on-premises. Preview features may have restricted functionality and aren't meant for production. You can create a new sandbox on 29.0 preview or schedule an update of an existing sandbox to it.
2. Watch the preview deadline. Microsoft says preview sandboxes are deleted automatically 30 days after 29.0 reaches GA (early November 2026) and can't be moved to another version. Don't put work you need to keep there.
3. Collect your rate history. For each vehicle category, list the rate, distance unit and effective dates. U.S. organizations following the IRS have at least two 2026 periods to enter.
4. Plan clean boundaries. Make each range end the day before the next begins, so there are no gaps or overlaps until Microsoft explains how it handles them.
5. Test the edge cases. Try trips on the last day of one period and the first day of the next, round trips, each vehicle type, and a claim with no vehicle type. Check the results by hand against your written policy.
6. Retest after GA. The feature may behave differently between preview and general availability.

The bigger picture​

This is a small item in a crowded release wave, and that makes sense. Microsoft is gradually filling Expense Agent's gaps against mature standalone expense tools, which have offered effective-dated, vehicle-specific rates for years.

The useful part is where the logic sits. An AI agent that pulls data from receipts is only as reliable as the rules behind it. If the agent uses the wrong mileage rate every time, it is simply wrong more often. Putting the rate logic in dated, auditable setup records, rather than an admin editing one number twice a year, is the right design.

The release comes as Microsoft changes how it publishes Business Central plans. The 29.0 documentation says Microsoft stopped publishing Release Plans in September 2026 and now puts new Business Central capabilities on the AI at Work roadmap. That roadmap is where entry 573254 appears, so administrators should keep an eye on it.

Bottom line: if your organization reimburses mileage at more than one rate, whether because of the IRS mid-year change, different vehicle classes or several countries, this update replaces a manual workaround. Test it in a sandbox, keep your date ranges clean, and wait for Microsoft's feature documentation before you rely on it for payroll-adjacent money.