Yes, you can send faxes using VoIP, although a fax machine can only be used with VoIP by plugging it into an analog adapter.
Whether you use VoIP for residential or business purposes, almost all virtual phone systems can receive fax messages. You either have to provide a phone number or create a separate extension, and your incoming faxes will appear in your phone system account as email messages with a PDF (the actual fax) attached to it.
Meanwhile, outbound faxing is not available for residential phone systems. When it comes to business VoIP, there are several options to choose from:
Unlimited faxing: usually part of the VoIP package, some providers offer full faxing capabilities off the bat.
Faxing as an add-on: More flexible VoIP companies may provide faxing as an add-on where you pay an extra monthly fee to send faxes. Depending on the provider, this add-on might provide unlimited faxing from the getgo or have a tiered approach where the monthly quota it offers depends on how much you pay.
Faxing on demand: As the name implies, faxing on demand is the option where you only pay for the faxes you send. This can be a great option for companies that need only to send the occasional fax.