We are going to discuss about this topic in brief and in order to understand the topic, let us see briefly about fax, VOIP service and combination of both. And I hope after reading this article, you will get an answer for this question. Everyone knows that fax is a short form for facsimile and it is a document sent over a telephone line. VOIP is a short form for voice over internet protocol and it is transmission technology for voice communication over internet protocol and it generally refers to the communication services that are transported through internet instead of pstn.Fax machines that are incorporated with VOIP service can be called as internet fax service and this online fax sends the fax via internet and not through public telephone switching network. Compressing fax signals differ from the compression of voice signal and for this purpose t.38 is created. Fax using VOIP is not sent to and fro from phone, it is sent to and fro through ip addresses. Let us see how the fax through VOIP works and we will also see its advantages and disadvantages. Through this VOIP faxing, the customer never gets a busy signal because you’re not using the pstn line so there is no possibility of busy signal.The advantages are, it Give your employees the freedom to send as many documents and to do business as often as they need, it reduces paper cost, phone cost, eliminates network problems, busy signals and no extra telephone line is required. Faxing over VOIP protocol needs some reliable accessing over ip protocol and proper software to support it. Generally VOIP are good with speech signals and it does not deal with fax over VOIP networks. Internet plays a major role in VOIP and VOIP faxing is less reliable than pstn because VOIP does not provide the mechanism to check whether the data packets are lost or delivered.Fax using VOIP has need to be increase a lot and in the fax using VOIP packets may be lost since we use the internet facility and if there is any error in connection, there is a chance for the loss of packets. If it is in voice it is adjustable, but in packets there should be no compromise and also there is a chance of power failure. Jitter, latency, redundancy are the other problems and they are well designed to digitize the voice signals, but it fails in digitizing the analog data. Sending quite big documents through VOIP may lead to loss of data and can show error messages which in turn may affect the business. It has low bit rate, unreliable and has some suppression and relativity in which the modem hesitate. As said above, t38 supports fax over VOIP and it needs VOIP gateway and ATA that supports t38. All the problems faced by fax using VOIP can be solved through the performance of t38.