Individual Master File
Individual Master File: The IRS computer system that holds the tax account of each individual taxpayer, recording returns, assessments, payments, credits and refunds by taxpayer identification number. Accounts that cannot be handled on the master file are kept on the Non-Master File (NMF).
What individual master file means
Put simply, individual master file is part of the working vocabulary of a civil case. The short definition above covers the usual meaning. Still, a specific rule, statute or contract can give it a narrower meaning. For that reason, check how it is used in your own documents.
Where individual master file comes up
The term is used across many kinds of cases. For example, you may see it in pleadings, motions and court orders. To see it in context, browse the motions and procedures library or the Learn the Law topics.
How to research the term
Start with the primary source. For example, if individual master file appears in a federal rule, read the rule itself and its official notes. After that, check your court’s local rules and any standing orders from the judge. In addition, search recent decisions from your own state or federal district. They show how courts read individual master file in practice. Because state rules often differ, our state procedures guide links to each state’s official rules. Above all, make sure the version you read is still in force.
You can read the current federal court rules online for free.
Related legal terms
- In propria persona: latin for "in one's own person." Appearing in court for yourself, without an attorney. Also called pro per or pro se.
- Incompetent: lacking the legal or mental ability to do something.
- Incorporation doctrine: the process by which the Supreme Court has held that most rights in the Bill of Rights bind the states through the Due Process Clause of the Fourteenth Amendment.
- Individual: a single human being.
Why precise terms matter
Courts read legal terms closely. As a result, knowing the exact meaning of a word helps you follow orders, rules and filings. Each glossary entry on Lawtopolis is short on purpose and links to the pages where the term is used.
Sources
Sources last reviewed: 2026-10-24
Lawtopolis provides legal information and education, not legal advice. Using this site does not create an attorney-client relationship. Laws and court rules vary by jurisdiction and change over time; verify every authority against the official source and consult a licensed attorney in your jurisdiction about your situation.