ValidationError

['ManagementForm data is missing or has been tampered with']

    if request.method == 'POST':

        formset = AddRecipeFormset(data=request.POST)

        if formset.is_valid(): …

            formset.save()

            return redirect(reverse_lazy("planner-home"))

Solution

Added {{ formset.management_form }} and <fieldset> tags to template.