susioma/ledger/admin.py

from django.contrib import admin
from ledger.models import Payment
from django.utils import timezone

def repay(modeladmin, request, queryset):
    queryset.update(repayment=timezone.now())

repay.short_description = "Mark selected payments as repaid"

class PaymentAdmin(admin.ModelAdmin):
    list_display = ["description", "amount", "date", "repayment"]
    ordering = ["date"]
    actions = [repay]

admin.site.register(Payment, PaymentAdmin)