Re: Calculations

in addition to what @Thomas said you need to first perform an aggregated sum on the payments model hence the need for ... loan.payments_set.aggregrate(models.Sum('amount')) the above returns the sum of all payment related to your loan instance from which you can now subtract from loan.amount_to_

Re: Adding extra registration fields to my user registration

there're two possible reasons for this: * you don't have those filled in your forms.py module or * your forms filled is not of the same case (upper or lower) with your request.Post[ ] query. but next time, try and add screenshot while asking question, its gives whoever that is responding more in