Hi There,
I have worked on billing probably utility application precisely for Energy, Electric bills and others for Europe regions. I can share example and reference on next level.
Second, looking at project it seems you like to build the on-line portal where user can pay the bills probably can track and have history as well. Default question which payment gateway we need to implement here. If Im not wrong then we need considered bank payment gateways as well.
Third, I proposed to develop the system using Laravel PHP frame work please let me know your thoughts as you have written ASP.net in skillsets.
Fourth, If you could provide reference website or document if you have any, I will have good grip on project.
Fifth, with few assumptions we are guessing we need 10 days while the cost will be around USD 500 but its just ballpark.
Thanks,
AspireWebs