Вы можете создать модель пользовательского профиля, например:
from django.db import models
from django.contrib.auth.models import User
TAX_PAYER = 'tax_payer'
TAX_OFFICIAL = 'tax_official'
USER_TYPE_CHOICES = (
('tax_payer', 'Tax Payer'),
('tax_official', 'Tax Official')
)
class UserProfile(User):
role = models.TextField(max_length=20, choices=USER_TYPE_CHOICES)