What is a billable expense?

A billable expense is a cost incurred on behalf of a client that will be passed through and invoiced for reimbursement, such as travel, materials, or third-party services. For professional service firms, tracking billable expenses ensures cost recovery and accurate client invoicing.

Key characteristics

• Incurred for client work

• Passed through to the client

• Must be tracked separately

• Included on client invoice

• May include markup

• Requires documentation

Why it matters for professional service firms

Billable expenses represent recoverable costs. Failing to track and bill them leaves money on the table. Professional service firms should have clear systems for capturing, documenting, and invoicing billable expenses promptly.

Real-world example

Kevin traveled for a client project: airfare $680, hotel $420, meals $85. Billable expense tracking: logged each expense with client code, attached receipts, and marked as billable. The month-end invoice included: professional fees $12,000 plus reimbursable expenses $1,185. Client agreement specified expenses billed at cost. Without tracking, $1,185 would have been absorbed as firm expense.