Faxing double sided can be tricky.
In most cases it can only be done through a fax machine with a document feeder or duplex printer (usually found on higher-level corporate equipment), or through computer-based fax such as fax software or an online fax service.
Understanding fax and “sides”
Fax can’t be “transmitted” double sided. All faxes are “sent” as a single sided document.
It is the physical fax machine that changes the single sided document to double sided (or the other way around if receiving the fax).
There is no encoding to say “make this fax transmission double sided” or “make this fax single sided.”
Sending a fax
… from a double sided document
To send a fax from a a double sided document, your options are
1) Use fax machine with a duplex document feeder (one that can read both sides of the page).
These are normally found on commercial level equipment (such as multifunction printer / scanner / copiers).
Some entry level / home office equipment without an auto-duplexing scanner but with the ability to do a software duplex will work as well. A software duplex is when each page is put onto the scanner glass, or the document is loaded into the feeder and scanned, then put in the opposite way and scanned again. The software in the equipment then mixes the pages into the proper order to send the document.
Check your user manuals.
2) Use a software-based faxing system (one such as fax software, an online fax service, or an advanced printer driver)
Many software based faxing systems will let you scan and pre-check your document. These systems will let you make sure the pages are in order, and may automatically collate a document that was scanned into a single-sided fax machine.
3) Copy and print out the second side of the document and mix the pages into the right places with the original document.
This is time consuming, but gets the job done. If without a printer, most fax machines have the ability to do a simple one-sided copy function.
Alternatively, you can copy the 2nd side of the document and attach it to the end of the original document. Not everyone receiving a document this way will enjoy it, and some may consider it an improperly sent document.
… to be received double sided
When sending a fax there is no way to designate whether the receiving fax machine will print it as single sided or double sided.
It is up to the receiving fax machine to determine how the document will be printed. Even a cover sheet marked with “print double sided please” will not help, as the cover sheet is part of the transmitted document and isn’t read until the entire fax is printed.
…from a double sided document to be received as double sided
See the two sections above.
Receiving a fax double sided
It is impossible for a receiving fax machine to understand whether the document was one sided or two sided. It can, however, print the document out as a two sided document if the fax machine has those capabilities.
… from a single sided document
To print a fax as a double sided document, you will need a fax machine with a duplexing printer.
These are typically found in commercial level equipment, such as multifunction copier / printer / scanners with a fax feature.
Check the user manual to set the faxes to print to double sided automatically.
A best practice is to make sure that there is also the ability to send faxes double sided – many people use fax as a quick way to receive a document, sign it, and send it back through the fax. While saving paper is good, without the ability to fax back a double sided document it can create a lot of user frustration and potentially mis-sent documents.
… from a double sided document
There is no way to designate whether the sent document was initially single-sided or double-sided.
If receiving a document that the sender said was sent as double sided, it is important to verify the document to make sure that there are no pages missing and that pages are in the proper order.
The fax cover sheet should included the number of pages that the fax transmission totalled.