A fax machine isn't needed to send a fax any more. An online fax service does the job instead: a website or app that turns your document into a fax signal and sends it down the phone network for you, much as a fax machine would, without one sitting on a desk.

Sending one this way just needs a phone, the document itself, and the recipient's fax number. The process is much the same on an iPhone as it is on Android, even though the screens you'll see differ slightly between the two, and it's worth checking the free options before reaching for a card.

Before you go any further, it's worth checking whether a fax is actually what's being asked for, or whether a signed PDF or a secure portal upload would do just as well. If a fax genuinely is required, sending it from your phone is usually faster than finding somewhere with a machine, and if you'd rather do it from a laptop instead, the same services work there too.

Before you open an app or a website, get three things ready. Doing that first means you are not hunting for a document halfway through the process.

• The document itself, as a photo or a PDF. A photo taken on your phone works fine as long as the page is flat, well lit, and the edges are not cut off. A PDF, such as a form you signed and saved from an email, usually comes out cleaner on the other end.
• The recipient's fax number, written exactly as it was given to you. If you are sending outside the UK, you will also need the international dialling prefix for that country.
• A few minutes to work through the steps and wait for a transmission confirmation, the message telling you the fax reached the other end. It does not take long, but it is not instant either.

If you are not yet certain a fax is actually required, it is worth settling that question first. Some solicitors, GP surgeries and insurers will accept a signed PDF by email instead, and checking is quicker than sending a fax you did not need to send. That question is covered in Do I Actually Need to Send a Fax?.

Sending a fax from your phone comes down to a short sequence: open the service, upload the document, enter the number, and send. None of it needs a fax machine, a landline, or anything installed beyond a browser or an app.

Sending the fax

1. Open the online fax service in your phone's browser, or in its app if you've installed one.
2. Upload the document. If you're photographing a paper page rather than using an existing PDF, take the photo in good light and check the text is sharp, since a blurred photo makes for a blurred fax at the other end.
3. Enter the recipient's fax number. If you're sending abroad, include the international dialling prefix first, the same as you would for a phone call.
4. Add a cover sheet if the service offers one and you want to include a note, or skip it if the recipient only needs the document itself.
5. Check the preview before you go further. This is your last chance to catch a page uploaded upside down, out of order, or cut off at the edge.
6. Send the fax.

Confirming it arrived

Once it's sent, the service should show a transmission confirmation, a receipt confirming the fax reached the number you sent it to. This usually appears within a few minutes, often by email as well as on screen, though it can take longer if the line at the other end is busy or the number is wrong.

Keep that confirmation if the fax matters for something formal, such as a court deadline or a document a solicitor has asked for. It's your record that the document was sent, in the same way a proof of postage is for something sent by post.

If you haven't yet worked out whether a fax is actually required, that's worth settling first: read Do I Actually Need to Send a Fax?. And if your phone's camera isn't giving you a clean scan, sending the same document from a computer instead may suit you better; see How to Send a Fax from Your Computer (UK).

Most online fax apps work the same way whether you're on an iPhone or an Android phone, but the two platforms handle a few things differently, and it's worth knowing before you install anything.

Getting the app onto your phone

On an iPhone you'll find fax apps through the App Store, signed in with your Apple ID. On Android it's the Google Play Store, signed in with your Google account. Some apps ask you to verify that account or add a payment method before you can send anything, even if the send itself is meant to be free. Read that screen before you tap through it.

Scanning the document

An iPhone can turn a paper document into a clean PDF using the Notes app's built-in scanner, without installing anything extra. Android phones don't have one built-in app that every model shares in the same way, so you're more likely to scan through Google Drive's scan feature or through the fax app itself. Either route works, but check the result before you send it. A photo taken at an angle, with a shadow across it, can come out unreadable on the other end.

Free tiers: what to check before you rely on one

A free tier on a fax app usually means you can send a document without paying, up to some limit, and only after creating an account. The limit and the sign-up steps vary by app and change over time, so the only way to know what you'll actually get is to open the app's own pricing or account page before you start.

• Whether sending is free outright, or only free as part of a trial that turns into a subscription if you don't cancel it
• Whether the free allowance is tied to your Apple ID or Google account, or resets if you create a new one
• Whether there's a limit on pages, and what happens if your document goes over it

If you'd rather avoid installing anything on your phone at all, sending from a browser on a computer is worth a look too, and works through the same kind of service. See how to send a fax from your computer for that route.