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The controllers.validators module provides regex-based validators for Mexican government-issued identifiers. These functions are used internally by the app — for example, when saving a Customer (RFC) or an Employee (CURP) — and can be imported directly into any custom Frappe app that needs to validate these identifiers before stamping a CFDI or saving a record.

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is_valid_rfc(rfc: str) → bool

Validates an RFC (Registro Federal de Contribuyentes), the Mexican federal taxpayer registration number issued by the SAT. Returns True if the RFC string matches the expected format, False otherwise.

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RFC structure

An RFC encodes the taxpayer’s name initials and date of birth (or incorporation date for companies) followed by a three-character homologation key:
SegmentLengthDescription
Name initials3–4 letters3 letters for legal entities; 4 letters for individuals
Birth / incorporation date6 digitsYYMMDD format
Homologation key3 charactersAlphanumeric (A-Z, 0-9) — assigned by the SAT
  • Legal entities (companies): 12-character RFC (3 letters + 6 digits + 3 chars)
  • Natural persons (individuals): 13-character RFC (4 letters + 6 digits + 3 chars)

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Usage

from erpnext_mexico_compliance.controllers.validators import is_valid_rfc

is_valid_rfc("XAXX010101000")    # True  — generic public RFC (Público en General)
is_valid_rfc("XEXX010101000")    # True  — generic foreign RFC
is_valid_rfc("ABC010101AB1")     # True  — company RFC (12 chars)
is_valid_rfc("INVALID")          # False — too short, no date segment
is_valid_rfc("abc010101ab1")     # False — lowercase not accepted

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Regex pattern

r"^([A-ZÑ]|\&){3,4}[0-9]{2}(0[1-9]|1[0-2])([12][0-9]|0[1-9]|3[01])[A-Z0-9]{3}$"
The pattern enforces:
  • Uppercase letters only (A-Z, Ñ, and & for the ampersand used in some company names)
  • A valid month segment (01–12)
  • A valid day segment (01–31) — note this is a format check, not a calendar check
  • An alphanumeric homologation key

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is_valid_curp(curp: str) → bool

Validates a CURP (Clave Única de Registro de Población), the 18-character personal identity code assigned by the Mexican government to every citizen and resident. Returns True if the CURP string matches the expected format, False otherwise.

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CURP structure

SegmentLengthDescription
First letter of first surname1 letter
First internal vowel of first surname1 vowel
First letter of second surname1 letter
First letter of given name1 letter
Date of birth6 digitsYYMMDD format
Gender1 letterH (hombre / male) or M (mujer / female)
State of birth2 lettersTwo-letter SAT state code (e.g. DF, NL, JC)
Internal consonants3 consonantsFirst internal consonant of each surname and given name
Check digits2 charactersHomonymy differentiator (alphanumeric) + verification digit

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Usage

from erpnext_mexico_compliance.controllers.validators import is_valid_curp

is_valid_curp("GOMC800101HDFNRR09")  # True
is_valid_curp("gomc800101hdfnrr09")  # False — lowercase not accepted
is_valid_curp("INVALID")             # False

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Regex pattern

The validator uses a verbose multi-line pattern compiled with re.VERBOSE: 
r"""^([A-Z][AEIOUX][A-Z]{2}
	\d{2}(?:0[1-9]|1[0-2])(?:0[1-9]|[12]\d|3[01])
	[HM]
	(?:AS|B[CS]|C[CLMSH]|D[FG]|G[TR]|HG|JC|M[CNS]|N[ETL]|OC|PL|Q[TR]|S[PLR]|T[CSL]|VZ|YN|ZS)
	[B-DF-HJ-NP-TV-Z]{3}
	[A-Z\d])(\d)$"""
The pattern encodes the complete list of valid two-letter Mexican state codes and restricts the consonant block to true consonants (excluding vowels and special characters). Because the pattern is compiled with re.VERBOSE, whitespace and line breaks inside the raw string are ignored during matching.

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is_match(pattern, string, flags=0) → bool

The underlying helper used by both is_valid_rfc and is_valid_curp. Compiles a regex pattern and returns True if the string fully matches it from start to end (re.match). 
from erpnext_mexico_compliance.controllers.validators import is_match

is_match(r"^[A-Z]{3}$", "ABC")   # True
is_match(r"^[A-Z]{3}$", "ABCD")  # False — too long
is_match(r"^[A-Z]{3}$", "abc")   # False — lowercase
You can use is_match directly in custom validators by passing any standard Python regex flags (e.g. re.IGNORECASE, re.VERBOSE).
These validators enforce format only — they verify that the string matches the structural rules defined by the SAT, but they do not check whether the RFC or CURP actually exists in any SAT registry. For RFC existence validation against the SAT, use the CFDI web service’s status endpoint.

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