Expense Reimbursement Guide: How It Works and How to Manage It

Even if you have a dedicated corporate card program, employees often end up spending their own money on business expenses. Perhaps they had to book an unexpected taxi, or they bought a prospective client dinner before closing a major deal. No matter what they spend their money on, they need to be reimbursed in short order.

Expense reimbursement isn’t as simple as it might seem. Employees submit receipts through email, approvals happen in Slack, managers track spending in spreadsheets, and accounting reconciles everything manually at month-end. The friction comes from disconnected systems that turn straightforward transactions into multi-step workflows. With hours spent chasing receipts, matching transactions to categories, the real cost can end up being a lot more than the expense.

This guide covers what expense reimbursement is, what expenses qualify, how the process works, the tax implications, and best practices for building a policy that works without creating administrative overhead. We’ll also review Slash, a business banking platform that makes the reimbursement process significantly easier for both employees and finance teams. Slash users can submit, review, and approve reimbursements directly inside the integrated dashboard.¹

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What is expense reimbursement?

Expense reimbursement is when an employer pays back employees for business-related costs they covered out-of-pocket. This happens when employees don't have a corporate card or when specific purchases fall outside normal card usage.

Reimbursements under a properly structured accountable plan are not considered wages, which means they're not subject to payroll taxes (Social Security, Medicare, federal and state unemployment taxes) and don't appear on the employee's W-2.

This distinction matters significantly because it affects both the employer's tax deductions and the employee's taxable income. An employee who gets reimbursed $5,000 for legitimate business travel expenses under an accountable plan pays zero tax on that $5,000. Under a non-accountable plan, that same $5,000 becomes taxable wages, potentially costing the employee $1,500-2,000 in additional taxes depending on their bracket.

Under non-accountable plans, reimbursements are treated as taxable wages. The IRS considers these payments taxable income, subject to income tax withholding and payroll taxes. What separates the two comes down to whether the business can prove the expense had a clear business purpose, whether proper documentation like itemized receipts exist, and whether any excess reimbursement was returned to the company within required timeframes.

What expenses are typically reimbursable?

While each company defines its own policy, four categories of reimbursable expenses appear consistently across most businesses. The specific dollar limits, approval requirements, and documentation standards vary by company size and industry, but the expense types themselves remain stable.

Travel and transportation

Business travel often generates the most reimbursement requests: flights, hotels, rental cars, parking, tolls, rideshares, mileage. The IRS sets standard mileage rates annually for business vehicle use, which most companies adopt.

Hotel stays require itemized receipts showing nightly rate, taxes, and incidental charges. Airfare reimbursements cover ticket costs but may exclude premium cabin upgrades unless documented business reasons exist. Ground transportation includes taxis, rideshares, public transit, and parking during business travel.

Business meals can include meals while traveling and meals with clients or prospects. Solo meals during travel may need just a receipt, while client meals typically require additional context, such as attendees, companies represented, business topics discussed.

Entertainment expenses may not be deductible under current U.S. tax rules. Companies should clarify which client-related expenses qualify based on current tax treatment rather than presenting entertainment as automatically reimbursable.

Meal reimbursements often follow per diem rate structures for extended travel. They may be limited to fixed daily amounts rather than individual receipts, simplifying administration while requiring employees to manage spending within allocated amounts.

Supplies, tools, and software

Office supplies, tools, software subscriptions, and equipment purchases employees make on behalf of the business qualify for reimbursement. This captures one-off purchases like replacement laptop chargers, specialty paper for client presentations, domain registrations for new projects, or project-specific software subscriptions that don't warrant company-wide licenses.

Companies often maintain approved vendor lists for consistent pricing and quality. When employees buy from approved vendors, reimbursement approval flows faster because finance teams already trust those relationships and know pricing is competitive. Purchasing outside approved vendors may require additional justification or manager pre-approval.

Larger equipment purchases typically require pre-approval to ensure they meet company standards and avoid situations where employees buy items incompatible with existing systems or that exceed budget allowances. Some companies issue equipment directly rather than reimbursing personal purchases to maintain asset tracking and ensure standardization.

Training and professional development

Professional development covers conferences, courses, certifications, and educational materials improving job-related skills. Most companies cap annual spending per employee and require manager approval to ensure training aligns with role requirements. Conference attendance includes registration, travel, hotels, and meals. Tuition reimbursement for degree programs typically operates under separate policies with stricter requirements.

The line between reimbursable and non-reimbursable is drawn by the company's written policy, which is why having one matters. Without clear documentation, every expense becomes a negotiation about whether it qualifies, creating inconsistency in how different employees and managers interpret what's allowed.

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How the expense reimbursement process works

The process follows a predictable sequence, but each step carries hidden inefficiencies when handled manually. Lost receipts, delayed approvals, coding errors, and payment processing delays turn what should be a straightforward workflow into a source of employee frustration and finance team overhead.

Incurring the expense

The process starts when employees pay for business expenses with personal funds, which should overall be a rare occurrence. If and when it does happen, employees need to capture documentation immediately before receipts are lost or details forgotten.

Documenting and collecting receipts

Receipt collection creates friction. Employees should save physical receipts, photograph them before they fade or get crumpled up, and/or forward email confirmations. Documentation requirements vary by expense type and amount. Slash makes this process easy by allowing employees to instantly send pictures of their receipts via a text thread. From there, admins can review reimbursement requests directly in the Slash dashboard, and the reimbursement is sent directly to the employee’s connected bank account once approved.

Missing receipts create downstream problems. Without proper documentation, finance can't substantiate expenses for audits, and reimbursements may not qualify for tax deduction. The business purpose often gets lost, since receipts show what was purchased but not why it was necessary.

Submitting the expense report

Employees gather receipts, fill in transaction details, categorize expenses, explain business purposes, and route reports to managers. Manually typing information from receipts into forms rather than automated capture from images or transactions.

Submission deadlines affect when employees get paid and when finance closes books. Missing windows means waiting entire additional cycles for reimbursement.

The approval process

Managers verify that spending aligns with policy and business purposes are legitimate. This catches violations like excessive expenses, unapproved vendors, personal expenses, and duplicates.

Multi-level approvals add layers slowing the process. Some expenses need department manager review, finance, review, and an executive sign-off above certain thresholds. Each step can add days between incurring expenses and receiving reimbursement.

Getting reimbursed

Finance teams batch approved expenses and issue payments via ACH, direct deposit, or checks. Payment timing depends on reimbursement cycles (weekly, bi-weekly, or monthly).

Processing delays happen with coding errors requiring manual correction, missing bank information, or insufficient funds. Accounting reconciliation matches reimbursed expenses to general ledger accounts, verifies coding, and files documentation. When done manually, this work can consume a lot of time.

Accountable vs. non-accountable plans: What you should know

An accountable plan must meet three conditions: the expense has a valid business purpose, it is properly documented, and any excess reimbursement is returned within a reasonable timeframe. When these requirements are met, reimbursements are not treated as taxable income for employees and remain deductible for the employer.

“Business connection” means the expense must be ordinary and necessary for the company’s operations. Personal expenses do not qualify, even if they occur during business travel. “Substantiation” requires itemized records showing the date, amount, vendor, and business purpose. Credit card statements alone are not sufficient, since they lack detail. If employees receive advances or allowances, any unused portion must be returned, typically within 120 days, or the full amount may be treated as taxable wages.

Non-accountable plans fail to meet one or more of these requirements. In those cases, reimbursements are treated as taxable income and subject to payroll taxes. This often happens when expenses are reimbursed without proper documentation or when flat allowances are provided without requiring employees to account for how the money is spent.

While the IRS does not require accountable plans, the tax implications of not having one can be significant. Employees may end up paying taxes on legitimate business expenses, and employers may take on additional payroll tax obligations.

Best practices for building an expense reimbursement policy

A policy doesn't need to be long; it needs to be unambiguous. An effective policy defines what's reimbursable, what documentation is required, who approves what, and when employees can expect payment. Here are some best practices:

Define eligible expenses clearly

List specific expense categories with dollar limits, pre-approval requirements, and restrictions. Make the list complete enough that employees can self-determine qualification without asking managers every time. Address gray areas explicitly: do coffee runs with team members count, or just formal client meals? Office decorations or only traditional supplies? Premium economy on international flights or just standard economy?

Require proper documentation

Specify adequate documentation for each expense type. Itemized receipts should show date, vendor, amount, and items. For mileage: origin, destination, miles, business purpose. For client meals: receipt plus attendee names/companies plus business topic.

Set minimum thresholds where detailed receipts become mandatory. Some accept bank statements under $25 but require itemized receipts above. Clarify acceptable formats, such as physical receipts, photographs, or email confirmations.

Set submission deadlines

Establish how soon after incurring expenses employees must submit for reimbursement. This timeframe is typically 30-60 days, but it’s always good to encourage quicker submissions. Shorter windows improve accuracy, while longer windows provide flexibility.

Communicate monthly or bi-weekly cutoffs determining which reimbursement batch expenses fall into. Explain late submission handling, such as rejections, ones that require special approval, or ones that get delayed to the next cycle.

Establish a clear approval chain

Document who approves what. Direct managers approve routine expenses to thresholds, with higher amounts requiring finance or executive approval. Make thresholds explicit, and specify backup approvers when primary managers are unavailable. Build escalation procedures for disputed expenses that might reroute to finance or human resources for policy interpretation.

Communicate reimbursement timelines

Tell employees when to expect payment after approval. They may receive same-day payments for urgent requests or weekly/bi-weekly batches for routine expenses. It’s always smart to explain the processing time and provide status visibility. Systems showing "submitted," "approved," "processing," and "paid" eliminate unnecessary status check requests.

Review and update the policy regularly

Review annually to ensure limits make sense, categories cover common expenses, and procedures match current tools. Incorporate feedback about friction points and update when tax regulations change. The most common policy gap is often the simple failure to communicate the policy to employees clearly. A comprehensive policy that nobody reads doesn't prevent any problems. Make the policy accessible in the systems employees already use, like their expense submission tools, onboarding materials, or team handbook.

Simplify expense reimbursement with Slash

Lost receipts, manual expense report entry, and delayed approvals exist because the tools don't talk to each other. Receipts live in employee email or photo libraries, expense reports sit in separate software, approvals happen through email or Slack threads, and accounting data lives in yet another system that requires manual entry to stay current.

Slash is a business banking platform that’s built expense reimbursement into the same platform that handles corporate cards, banking, and accounting automation. Purchases with the Slash Visa® Platinum Card trigger automated receipt requests based on configured policies. When a transaction posts, employees instantly receive a text message prompting them to upload the receipt and confirm the business purpose.

All out-of-pocket reimbursable expenses are submitted and approved from the same dashboard that shows card spending, banking activity, and budget utilization. From there, approved reimbursements are paid directly through the platform without requiring finance teams to export data and process payments through separate banking systems.

All transactions sync to accounting software like QuickBooks Online, Xero, or Sage Intacct through automated mapping rules. Card purchases, reimbursed expenses, vendor payments, and more all flow to the right general ledger accounts without manual categorization or data entry. The system takes your categorization decisions and applies them to your transactions, reducing the manual coding work that typically consumes hours each month. Not to mention, each business purchase made with the Slash card can earn up to 2% cash back.

Other helpful Slash features include:

AI-powered finance: Our platform comes with Twin, a built-in AI agent that can be prompted with natural language to complete complex tasks. Users can ask it to create cards, pay invoices, review your cash flow, and much more.
Working capital financing: Access short-term financing with flexible 30-, 60-, or 90-day repayment terms to help bridge cash flow gaps.⁵
High-yield treasury: Earn up to 3.82% annualized yield on idle funds with money market investments from BlackRock and Morgan Stanley, managed directly within your Slash account.⁶
Native cryptocurrency support: Hold, send, and receive USD-pegged stablecoins USDC and USDT across eight supported blockchains for faster, lower-cost global payments.⁴
Diverse payment methods: Slash supports a wide range of payments, including card spend, global ACH, international wire transfers to over 180 countries via SWIFT, and real-time domestic payments through RTP and FedNow.

Managing employee expenses shouldn't require stitching together separate systems for cards, reimbursements, approvals, and accounting. Start managing your expenses with Slash.

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FAQs

What are the IRS requirements for expense reimbursements?

IRS requirements for tax-free expense reimbursements necessitate an "accountable plan". This requires employees to document business-related expenses (amount, time, place, purpose) with receipts within 60 days and return any excess advances within 120 days. Failure to meet these, such as missing receipts, makes reimbursements taxable income.

Do employee reimbursements need to go through payroll?

It depends on whether the reimbursements are taxable. You may pay outside of payroll when reimbursements qualify under an accountable plan, while those that don't qualify are taxable and should be routed through payroll.

How do mileage reimbursements work?

Mileage pay is a reimbursement method where employers pay employees a set rate per mile for using personal vehicles for business purposes. Mileage reimbursements cover gas, maintenance, and insurance, usually based on the IRS standard rate (e.g., 70 cents per mile in 2025). Employees track work-related miles and submit reports, generally excluding regular commutes.