Skip to main content

​
GenerarCUF

Generates the complete CUF (Código Único de Factura - Unique Invoice Code) for an invoice according to Bolivian tax authority specifications. The CUF is a unique identifier that combines invoice metadata with a verification digit and is encoded in hexadecimal format. It includes a control code (CUFD) to ensure authenticity.

​
Function Signature

func GenerarCUF(
    nit int64,
    fechaHora time.Time,
    sucursal int,
    modalidad int,
    tipoEmision int,
    tipoFactura int,
    tipoDocumentoSector int,
    numeroFactura int,
    puntoVenta int,
    codigoControl string,
) (string, error)

​
Parameters

​
nit
int64
required
Tax identification number (NIT) of the issuer. Formatted to 13 digits.
​
fechaHora
time.Time
required
Invoice date and time. Formatted as yyyyMMddHHmmssSSS (17 digits).
​
sucursal
int
required
Branch office code. Formatted to 4 digits.
​
modalidad
int
required
Invoice modality code. Formatted to 1 digit.
​
tipoEmision
int
required
Emission type code. Formatted to 1 digit.
​
tipoFactura
int
required
Invoice type code. Formatted to 1 digit.
​
tipoDocumentoSector
int
required
Document sector type code. Formatted to 2 digits.
​
numeroFactura
int
required
Sequential invoice number. Formatted to 10 digits.
​
puntoVenta
int
required
Point of sale code. Formatted to 4 digits.
​
codigoControl
string
required
Control code (CUFD) obtained from tax authority authorization.

​
Returns

​
cuf
string
The complete CUF in hexadecimal format with the control code appended.
​
error
error
Error if CUF generation fails.

​
CUF Generation Algorithm

The CUF is generated through the following steps:
  1. Format Fields: All input parameters are formatted to fixed-length strings with leading zeros:
    • NIT: 13 digits
    • Date/Time: 17 digits (yyyyMMddHHmmssSSS)
    • Branch: 4 digits
    • Modality: 1 digit
    • Emission Type: 1 digit
    • Invoice Type: 1 digit
    • Document Sector: 2 digits
    • Invoice Number: 10 digits
    • Point of Sale: 4 digits
  2. Concatenate: All formatted fields are concatenated into a single numeric string (53 digits total).
  3. Calculate Verification Digit: A Module 11 algorithm is applied to calculate a verification digit, which is appended to the string (54 digits total).
  4. Convert to Hexadecimal: The numeric string is converted to hexadecimal (base 16) and converted to uppercase.
  5. Append Control Code: The CUFD control code is appended to create the final CUF.

​
Verification Digit Calculation

The Module 11 algorithm (calculaDigitoMod11) calculates the verification digit:
  • Iterates through the string from right to left
  • Multiplies each digit by a factor (2-9, cycling)
  • Sums all products
  • Applies modulo 11 to the sum
  • Returns the verification digit (special handling for 10→1, 11→0)

​
Example

package main

import (
    "fmt"
    "log"
    "time"
    
    "github.com/amvi88/go-siat/pkg/util"
)

func main() {
    // Invoice parameters
    nit := int64(1234567890123)
    fechaHora := time.Now()
    sucursal := 0
    modalidad := 1
    tipoEmision := 1
    tipoFactura := 1
    tipoDocumentoSector := 1
    numeroFactura := 1
    puntoVenta := 0
    codigoControl := "ABC123DEF456"
    
    // Generate CUF
    cuf, err := util.GenerarCUF(
        nit,
        fechaHora,
        sucursal,
        modalidad,
        tipoEmision,
        tipoFactura,
        tipoDocumentoSector,
        numeroFactura,
        puntoVenta,
        codigoControl,
    )
    if err != nil {
        log.Fatalf("Error generating CUF: %v", err)
    }
    
    fmt.Printf("Generated CUF: %s\n", cuf)
    // Output: Generated CUF: 3F8A2B1C4D5E6F7A8B9C0D1E2F3A4B5CABC123DEF456
}

​
Notes

  • The CUF must be unique for each invoice
  • The control code (CUFD) must be obtained from the tax authority before generating invoices
  • All numeric fields are zero-padded to their required length
  • The date/time must include milliseconds
  • The final CUF is returned in uppercase hexadecimal format
  • XML Signing - Sign invoices with digital certificates

Build docs developers (and LLMs) love

Get started for freeTalk to us