I have encountered this problem just recently and I solved it by adding a hidden field on every form and getting that hidden value to determine what form was submitted by using an if condition in views
Here's how I did it using CBV.
views.py
class ContactUsView(TemplateView):
    template_name = 'yourtemplate.html'
    def get(self, request, *args, **kwargs):
        inquiry_form = InquiryForm(self.request.GET or None, prefix='inquiry_form')
        complaint_form = ComplaintForm(self.request.GET or None, prefix='complaint_form')
        context = self.get_context_data(**kwargs)
        context['complaint_form'] = complaint_form
        context['inquiry_form'] = inquiry_form
        return self.render_to_response(context)
    def post(self, request):
        # instantiate all unique forms (using prefix) as unbound
        inquiry_form = InquiryForm(prefix='inquiry_form')
        complaint_form = ComplaintForm(prefix='complaint_form')
        # determine which form is submitting (based on hidden input called 'action')
        action = self.request.POST['action']
        # bind to POST and process the correct form
        if action == 'inquiry':
            inquiry_form = InquiryForm(data=request.POST, prefix='inquiry_form')
            if inquiry_form.is_valid():
                # Your logic here
                return self.render_to_response(
                    self.get_context_data(
                        inquiry_form=inquiry_form,
                        complaint_form=complaint_form,
                    )
                )
            messages.error(self.request,
                           'Inquiry form is invalid.')
        elif action == 'complaint':
            complaint_form = ComplaintForm(data=request.POST, prefix='complaint_form')
            if complaint_form.is_valid():
                # Your logic here
                return self.render_to_response(
                    self.get_context_data(
                        inquiry_form=inquiry_form,
                        complaint_form=complaint_form,
                    )
                )
            messages.error(self.request,
                           'Complaint form is invalid.')
        # prep context
        context = {
            'inquiry_form': inquiry_form,
            'complaint_form': complaint_form,
        }
        return render(request, self.template_name, context)
yourtemplate.html
<!-- First Form -->
<form action="" method="post" role="form">
    {% csrf_token %}
    <input type='hidden' name='action' value='inquiry'>
    {{ form1 }}
    <button type="submit" title="Send Inquiry">Send Inquiry</button>
</form>
<!-- Second Form -->
<form action="" method="post" role="form">
    {% csrf_token %}
    <input type='hidden' name='action' value='complaint'>
    {{ form2 }}
    <button type="submit" title="Send Complaint">Send Complaint</button>
</form>
As you can see there's a hidden value in every form named 'action', that will be the one to determine which form was submitted.