FAR Part 31 Expense Management: Allowable vs Unallowable

In the commercial world, a lost receipt or a misclassified expense is a minor tax headache. In the world of government contracting (GovCon), it is a compliance crisis. If your team is still charging travel, meals, and materials to an entry-level accounting app or tracking them on manual spreadsheets, you aren’t just losing operational efficiency, you are actively risking your business. 

For federal contractors, expense management is fundamentally different from generic corporate expense tracking. The Defense Contract Audit Agency (DCAA) and the Federal Acquisition Regulation (FAR) dictate strict rules about what types of money your firm can spend, how those expenditures are categorized, and who ultimately foots the bill. 

If your back office cannot separate a billable project expense from an unallowable corporate expense down to the exact penny, you risk failing your next audit, destroying your indirect rates, and getting banned from bidding on future cost-type contracts. 

This comprehensive guide breaks down the high stakes of GovCon expense tracking, the regulatory framework of FAR Part 31, common pitfalls that sink small contractors, and how to implement a modern, automated system that keeps your firm continuously audit-ready.  

What Makes GovCon Expense Management Different?

In a standard commercial business, an expense is simply an operational cost that offsets revenue. If the business owner wants to buy a premium steak dinner for a prospective client, it is classified as a business meal, written off at the tax deadline, and forgotten. 

In government contracting, that same steak dinner is subject to intense scrutiny under FAR Part 31 (Contract Cost Principles and Procedures). The government breaks down every single dollar your firm spends into three strict compliance pillars: 

1. Is the Cost Reasonable? 

Under FAR 31.201-3, a cost is considered reasonable if, in its nature and amount, it does not exceed that which would be incurred by a prudent person in the conduct of competitive business. If your consultant rents a compact car for a site visit, that is reasonable. If they rent a luxury sports car, the DCAA will flag the cost as unreasonable, forcing your firm to absorb the difference.

2. Is the Cost Allocable? 

Allocability (FAR 31.201-4) means the expense must directly deliver value to the contract or overhead pool it was charged to. If you purchase software licenses exclusively for engineers working on "Contract A", that cost cannot be allocated to "Contract B" or buried inside your general overhead pool. 

3. Is the Cost Allowable? 

This is the ultimate test in GovCon accounting. A cost can be perfectly reasonable and fully allocable, but if federal regulations declare it unallowable, the government will not pay for it, nor can it be used to calculate your indirect rates. 

Allowable vs. Unallowable Expenses: The Golden Line 

Understanding the distinction between allowable and unallowable costs is the core requirement of any DCAA-compliant expense tracking protocol. The government splits your expenditures into distinct financial categories: 

Direct Allowable Expenses: These are costs that can be tied directly to a specific contract deliverable. Examples include: 

• Project-specific travel (flights, lodging, per diems matching federal limits). 

• Materials purchased exclusively for the execution of a contract. 

• Subcontractor labor dedicated to a contract task. 

Indirect Allowable Expenses: These are costs necessary to run your business that support government work as a whole. They are allocated into your fringe, overhead, or G&A (General and Administrative) cost pools: 

• Standard internal office supplies. 

• Approved corporate cell phone plans for technical staff. 

• Required training and certifications for contract personnel. 

Expressly Unallowable Expenses: FAR Part 31 lists dozens of expenses that the government refuses to subsidize under any circumstance. These must be segregated into completely separate accounts (often referred to as 9000-series accounts) so that they never touch a government invoice or an indirect cost calculation. 

Common unallowable expenses include: 

• Alcohol: Any beverage purchase containing alcohol is strictly unallowable. 

• Entertainment: Concert tickets, sporting events, and golf outings, even if done for client retention, are completely unallowable. 

• Bad Debts: Losses arising from uncollectible customer accounts. 

• Lobbying & Political Contributions: Any funds spent attempting to influence local, state, or federal legislation. 

• Interest Expense: Financing costs and interest on corporate credit lines. 

The Critical Role of the JTR and Per Diems 

When it comes to travel, the DCAA doesn't allow contractors to self-police what counts as an acceptable cost. All travel expenses must align precisely with the Joint Travel Regulations (JTR) and the per diem rates set by the General Services Administration (GSA). 

Lodging and M&IE Limits: Every zip code in the United States has a maximum allowable daily rate for lodging, as well as a cap for Meals and Incidental Expenses (M&IE). If a consultant travels to Washington, D.C., their hotel cap might be $250 per night during peak season. If they choose to stay at a luxury resort for $450 per night, your firm cannot bill the government for the remaining $200, nor can you place that excess inside your indirect cost pools. 

The "First and Last Day" Rule: The JTR mandates that on the first and last day of travel, employees are only entitled to 75% of the standard M&IE per diem rate. A generic corporate expense application has no concept of this rule; it will happily approve 100% of the meal cap, creating an immediate compliance variance that a DCAA auditor will flag instantly during an audit. 

How Sloppy Expense Tracking Triggers DCAA Audit Failures 

When small government contractors undergo an SF-1408 pre-award accounting system survey, the auditor is specifically examining your system’s ability to segregate costs. Sloppy expense tracking is one of the leading reasons promising firms fail this evaluation. 

The Myth of Deleting Unallowable Receipts:

A major mistake made by firms transitioning from commercial work to GovCon is assuming that if an expense is unallowable, they should simply pay for it out of pocket and delete it from the accounting system. 

This is a critical audit failure. The DCAA requires a complete audit trail of all corporate spending. Unallowable expenses must be captured, approved, recorded in your general ledger, and explicitly excluded from government billings. If an auditor reviews your corporate credit card statements and sees transactions that do not appear anywhere in your ledger, it looks like you are actively concealing costs. 

The Impact on Your Indirect Rates: 

Your indirect rates (fringe, overhead, G&A) are calculated by dividing your indirect cost pools by your total direct cost bases. If unallowable costs mistakenly leak into an allowable indirect pool, your calculated rate becomes artificially inflated. 

If you use that inflated rate to bill the government on a cost-plus contract, you are overcharging the taxpayer. When the DCAA uncovers this during a retrospective incurred cost audit, you won't just have to pay the money back, you could face structural penalties, interest, and fraud investigations. 

5 Critical Expense Management Mistakes Small GovCons Make 

1. Relying on Commercial Expense Software: Generic accounting tools are designed for commercial businesses. They lack native logic for GSA per diem integration, the JTR 75% travel day rule, and automated segregation of FAR 31 unallowable costs. Relying on them requires your accounting team to manually cross-reference every single line item against federal tables. 

3. Lacking an Explicit Written Travel & Expense Policy: The DCAA requires your firm to maintain documented internal controls. If you do not have a written corporate travel policy that explicitly outlines adherence to FAR Part 31 and GSA per diems, the auditor can rule your accounting system inadequate, regardless of how clean your software appears. 

4. Co-mingling Direct and Indirect Materials: If an employee goes to a local supplier and buys tools for a direct contract alongside general maintenance supplies for the home office, placing both items on a single expense report under a generic "Supplies" account violates the core principles of cost segregation. Every item must be split into its own line item and routed to its respective project or pool code. 

5. Missing Supervisor Approval Trails: Every expense report submitted by an employee must be digitally signed by both the employee and an authorized supervisor. Furthermore, if a change is made to an expense allocation after submission, the system must retain a permanent, immutable record of who made the change, when it occurred, and why it was modified. 

How Modern GovCon Software Automates Expense Tracking 

Historically, managing far part 31 unallowable costs required a massive administrative footprint: rows of filing cabinets filled with paper receipts, complex Excel matrices, and full-time compliance consultants. Modern, project-based ERP platforms have changed the landscape entirely. 

1. Native Mobile Receipt Capture with Project Tagging: Modern platforms feature native iOS and Android mobile apps that allow consultants to take a photo of a receipt right at the dinner table. The software immediately forces them to link that receipt to a specific contract code, task order, or internal overhead line before it can even be submitted. 

2. Built-In GSA Per Diem Guards: Advanced govcon travel expense software connects directly to live GSA databases via API. When an employee logs a hotel stay in San Diego, the system automatically checks the date against federal lodging caps for that area. If the charge exceeds the limit, the system instantly flags the overage, automatically splitting the allowable portion to the project code and the unallowable remainder to the firm's 9000-series account. 

3. Automated Corporate Credit Card Matching: Instead of waiting until the end of the month for manual statement reconciliation, cloud-native ERP platforms pull live credit card feeds daily. The software automatically cross-references card transactions with submitted mobile receipts, highlighting discrepancies instantly and ensuring that billable costs are captured within the correct accounting period. 

4. Seamless Integration with the General Ledger: The true power of an integrated system like SumX ERP is that your expense software isn't siloed from your accounting package. When an expense report is certified, the data flows seamlessly into your labor distribution ledger and automatically feeds into your real-time indirect cost pool calculations. This eliminates duplicate data entry, reduces human error, and keeps your firm continuously prepared for an audit. 

FAQ: GovCon Expense Management 

Q: What does FAR Part 31 say about expense tracking? 

FAR Part 31 outlines the specific cost principles governing federal contracts. It mandates that any cost charged to the government must be reasonable, allocable, and allowable. It explicitly lists multiple items (like alcohol and entertainment) that are completely unallowable and must be structurally isolated from government billing. 

Q: Can I use standard QuickBooks for GovCon expense tracking? 

No. Standard QuickBooks does not have the native structural capacity to link expense entries to multi-layered project hierarchies, automatically compute indirect cost pool allocations, or enforce GSA per diem restrictions and DCAA-required timekeeping audit logs. 

Q: What happens if an employee accidentally bills an unallowable cost to a contract? 

If your internal controls catch the error before invoicing, you simply reclassify the expense to an unallowable ledger account. If the error is discovered later by a DCAA auditor during an incurred cost submission review, your firm may face financial repayment obligations, interest charges, and systemic penalties. 

Q: What is the JTR 75% rule for travel days? 

The Joint Travel Regulations dictate that on the first and last day of official business travel, an employee's allowable Meals and Incidental Expenses (M&IE) allowance is limited to 75% of the standard daily per diem cap for that specific destination. 

Q: How much does a DCAA-compliant expense system cost? 

Legacy enterprise accounting platforms often require tens of thousands of dollars in upfront implementation fees. However, modern cloud-native systems like SumX ERP integrate compliant expense tracking directly into their core project-accounting framework for an accessible rate of $30 per employee per month. 

Conclusion: Protect Your Margins and Your Compliance 

In government contracting, cash flow is directly tied to your administrative accuracy. Every hour your finance team spends manually separating unallowable costs from allowable receipts is a waste of specialized overhead. Every billable expense that slips through the cracks due to a missing receipt is pure profit leaking out of your firm. 

By transitioning from disconnected, manual spreadsheets to an integrated, project-based framework like SumX ERP, you protect both your contract margins and your compliance posture. You gain real-time visibility into project burn rates, eliminate manual card reconciliation bottlenecks, and secure the peace of mind that comes from knowing your books are continuously audit-ready. 

Stop managing federal compliance with commercial tools. 

See how SumX automates GovCon expense tracking → Request a demo