- OTCQB
- Obamacare
- Obligor
- Offer in Compromise
- Offline Debit Card
- Offset Mortgage
- Oligarch
- Ombudsman
- On-Us Item
- One-Pay Lease
- Online Banking
- Online Bill Pay
- Online Savings Account
- Open Enrollment
- Open Interest in Trading
- Open-End Lease
- Open-End Mortgage
- Open-Ended Account
- Open-Loop Card
- Operating Expenses
- Opportunity Cost
- Opportunity Zone
- Option Adjustable-Rate Mortgage
- Option Assignment
- Options Roll Up
- Order Book
- Ordinary Income
- Ordinary and Necessary Expenses
- Other Income on Form 1040
- Out-of-Pocket Damages
- Out-of-Pocket Maximum
- Outstanding Shares
- Over-the-Counter (OTC) Market
- Overfunded Pension Plan
- Overheated Economy
- Overtrading
- Owner Occupant