Harold Finch often uses an alias when investigating a person or a location.

While his true birth name is still a mystery, he commonly uses Harold as a first name. His earliest records ("Wolf and Cub") list him as Harold Wren, which is also the name known to his best friend Nathan Ingram. Reese, Fusco, Carter, Alicia Corwin, Leon Tao, and Samantha Shaw know him as Harold Finch.

Image	Episode	Name	Occupation
	"Ghosts"	Arthur Bellenger	Insurance agent
	Acts as an insurance agent of Liberty State Mutual to talk to Theresa Whitaker's aunt in order to find out more about her disappearance.
	"Mission Creep" "Cura Te Ipsum"	Norman Burdett	Paralegal
	Works at Marmostein Ribner. He gives this name to the police when they interview him about the evidence locker robbery he witnessed when he went there to warn Reese about being set up. ("Mission Creep") He also meets Carter for the first time face to face under this name.
	"Judgment"	Walt Trowbridge	IT technician
	Poses as IT staff at One State Bank who checks account data after the bank's database was alledgedly hacked.
	"The Fix"	Mr. Partridge	Investor
	Uses this alias to meet with Mark Lawson of Virtanen Pharmaceuticals to talk about his recent investments in the company and to plant a bug in their office.
	"Number Crunch"	Thomas Paine	Blogger
	Uses this alias to confront Jim Hallen about the Cayman charities and the money that has been embezzled by Hallen and Davis Bannerman.
	"Legacy"	N/A	DFS tech support
	Gains access to the office to alter the function of the office's shredder so that it scans documents instead of destroying them allowing him to get proof of suspected misconduct.
	"Wolf and Cub" "Shadow Box"	Harold Wren	Insurance underwriter
	Finch is been using this alias since 1976 ("Wolf and Cub") when he studied at MIT. He is currently working under this name at Universal Heritage Insurance. Nathan Ingram and his son both know Finch under this alias.
	"Risk" "Triggerman" "Critical" "Til Death"	Harold Crane	Investor, donor, assistant surgeon
	First used when Finch posed as a secret investor to help Adam Saunders get back the money he lost by initiating a buying frenzy at Baylor Zimm. Finch uses this alias again when he visits Elias in prison to ask for his help in calling off the hit on Riley Cavanaugh. When Dr. Madeleine Enright's number came up, Finch used the alias to gain access to the hospital where she worked and also helped her to save a patient's life. When the Machine produced Daniel and Sabrina Drake's numbers, Finch used the alias under the guise of investing in a new imprint and sent Reese posing as his employee to keep an eye on the couple in their publishing company.
	"Risk"	N/A	SEC investigator
	Talks to Adam Saunders' uncle about his investments in a company called Tritek.
	"Baby Blue"	Dr. Tillman	Pediatrician
	Uses the name of a former person of interest as an alias to gain access to Leila Smith, a new PoI at St. Raymond's Clinic. Eventually he takes the baby and protects it from being abducted.
	"Baby Blue"	Lucas Bennett	DFS agent
	Poses as an employee of the Department of Family Services to talk to the grandparents of Leila Smith and to find out more about her mother.
	"Identity Crisis"	Harold Crow	Private investigator
	Approaches the female Jordan Hester under this alias because he thinks that she might be in danger because someone who stole her identity. He tells her that he had been hired by another victim of identity theft.
	"No Good Deed"	N/A	Delivery Man
	Delivers a bugged coffeemaker to Henry Peck's office in order to monitor his activities in the office.
	"The High Road"	Harold	Technician
	Works for John Campbell's private security systems company and installs a camera on Graham Wyler's house.
	"2πR"	Harold Swift	High School teacher
	Goes undercover as a math teacher in a school in Brooklyn to keep an eye on Caleb Phipps.
	"Booked Solid"	Harold	Concierge
	Started to work as concierge at the Coronet Hotel when one of their maids' number came up.
	"Proteus"	Harold Gull	Storm chaser
	Has been a certified member of the National Storm Chasers and Spotters Association for over ten years. He also has a pilot's license.
	"All In"	Harold Quail	IRS Agent
	Uses this alias when Lou Mitchell realizes that he is being followed.
	"Trojan Horse"	Harold Starling	IT Guy
	Is an IT guy at Rylatech, a technology firm plagued by espionage.
	"Zero Day"	Mr. Ostrich	Unknown
	This pseudonym comes up when he is discussing his pending engagement to Grace Hendricks with Nathan Ingram