models.py

class SpendingCategory(models.Model):
    category = models.CharField(max_length=32, null=False)

    def __str__(self):
        return self.category

    class Meta:
        verbose_name_plural = "Spending Categories"


class Spending(models.Model):
    name = models.CharField(max_length=128)
    date = models.DateField(default=datetime.date.today)
    amount = models.FloatField()
    month = models.ForeignKey(Month, on_delete=models.CASCADE)
    category = models.ForeignKey(SpendingCategory, on_delete=models.CASCADE)
    paid = models.BooleanField(default=False)