General information, not legal advice.

Four identifiers, not one

A single matter in an Indian court can carry several identifiers at once:

1. Filing number. In district courts on the eCourts system, a filing number and year are given when the papers are first filed, before scrutiny.
2. Registration (case) number. After the registry accepts the filing, the case gets a case type, a number and a year, for example CS 245/2023. This is the number printed on cause lists and order sheets.
3. CNR number. A 16-character code that is unique nationally and stays the same for the life of a district court case, even if the case is transferred.
4. Diary number. At the Supreme Court, a diary number is assigned on filing, and a registration number follows if and when the matter is registered.

A related number, the FIR number, belongs to the police station. It is the station plus a serial number and year, and should never be mixed with any of the above.

The case number: type, number, year

The registration number has three parts:

• Case type. A short code from the court's own list of case types. Common examples include CS or OS for civil or original suits, WP for writ petitions and CRA or CRL.A for criminal appeals. These lists are local. Each High Court and each district court establishment keeps its own, and the same matter type can be coded differently in different states.
• Number. A serial number, usually restarting each year for that case type in that court.
• Year. The year of registration.

The important point for data work is that CS 245/2023 is not unique. Hundreds of courts can have a civil suit 245 of 2023. A case number only identifies a case together with its court, meaning the state, district and court establishment, or the High Court and bench.

The CNR, briefly

For district courts, the CNR solves the uniqueness problem. It combines codes for state, district and establishment with a serial number and a year into one 16-character string, for example XXYY01 followed by six digits and a four-digit year. If you can get a CNR, use it as the primary key and treat the case number as a display field.

Normalising user input

People type case numbers in many ways. A forgiving parser can reduce most variants to a canonical form:

import re

PATTERN = re.compile(
    r"""^\s*
        (?P<type>[A-Z][A-Z.()\s]*?)      # case type, e.g. CS, C.S., CRL.A
        \s*(?:NO\.?)?\s*
        (?P<num>\d+)                     # serial number
        \s*(?:/|-|OF)\s*
        (?P<year>\d{4})                  # four-digit year
        \s*$""",
    re.IGNORECASE | re.VERBOSE,
)

def normalise(raw: str):
    m = PATTERN.match(raw.upper())
    if not m:
        return None
    case_type = re.sub(r"[.\s]", "", m["type"])   # "C.S." -> "CS"
    return case_type, int(m["num"]), int(m["year"])

normalise("C.S. No. 245 of 2023")   # ('CS', 245, 2023)
normalise("wp 1234/2024")           # ('WP', 1234, 2024)

Some practical rules:

• Strip dots and spaces from the type, but keep a mapping table per court. CRL.A and CRLA are probably the same type, but CRA might not be, depending on the court.
• Store the number as an integer and pad it with zeros only when displaying.
• Require a four-digit year. Two-digit years such as /23 are ambiguous in old records.
• Detect CNRs separately. A 16-character alphanumeric string with no separators is almost certainly a CNR and should skip the case-number parser.

Modelling it in a database

A workable schema keeps the court and the identifiers separate:

CREATE TABLE cases (
  cnr            CHAR(16) UNIQUE,        -- null for courts without CNR
  court_id       INTEGER NOT NULL,       -- state + district + establishment
  case_type_code VARCHAR(20) NOT NULL,   -- as used by that court
  case_number    INTEGER NOT NULL,
  case_year      SMALLINT NOT NULL,
  filing_number  INTEGER,
  filing_year    SMALLINT,
  UNIQUE (court_id, case_type_code, case_number, case_year)
);

The composite unique key reflects how courts actually number cases. Keeping the filing number separate means you can still trace a matter before it is registered.

Where this shows up in practice

Search tools built on court data have to accept all these forms. MyCaseStatus.in's case search lets users look a case up by CNR number, party name or advocate name, which avoids much of the ambiguity in free-typed case numbers. Even so, it is worth confirming important dates against the court's own record.