What is the PSTN switch off?

The Public Switched Telephone Network (PSTN) will be switched off on January 31, 2027.

After that date, anyone still relying on copper telephone wires to make calls will lose connection unless they switch to digital lines.

Although the official switch-off date isn’t until early 2027, PSTN lines are becoming increasingly fragile and unreliable. In fact, there were over 2,600 major incidents on the PSTN between April 2024 and March 2025.

The connectivity problems are likely to continue up until the switch off, so to avoid further issues, Openreach is encouraging businesses to switch by the end of December 2025.

In the UK, over two thirds of landlines have so far been upgraded to Voice over Internet Protocol (VoIP), but that leaves many still in need of new phone systems.

Essentially, the earlier you switch, the better.

How does the PSTN work?

The PSTN works by transmitting voice calls over an extensive network of telephone exchanges and copper wire transmission lines.

When calls are made on a landline, they connect to a local exchange, which in turn communicates with trunk exchanges and main hubs before connecting with the recipient’s local exchange.

Typically, lines within a local exchange share the same area code. For any calls that aren’t local, the area code needs to be included.

This is an analogue technology that has been around for over a century, so it’s no wonder we’ve reached the point where the lines need to be retired.

Why will the PSTN be switched off?

There are several reasons for the PSTN switch off, namely:

1. Technological advancements — There are now digital communication technologies that don’t use the PSTN which provide more efficient and cost-effective services.
2. Maintenance costs — Traditional copper wires have become unreliable, but suppliers are no longer manufacturing the parts required for their maintenance and repairs. As such, the telecoms industry is struggling to fix connection issues, and the cost implications are outweighing the benefits of keeping the system going.
3. Decreased usage — With more people switching to digital and mobile services, traditional landlines are less frequently used.

The PSTN switch off in the UK follows similar trends in other countries. Estonia and the Netherlands have already retired their copper wires, while Germany, Japan and Sweden are in the process of doing so.

Along with the PSTN, the Integrated Services Digital Network (ISDN) is also getting retired.

ISDN switch off

ISDN technology uses the PSTN to digitally transmit voice, video and data. It allows multiple voice calls to be transmitted at the same time, so it has previously been a popular option for office phone systems.

The ISDN had been seen as a solution for digital data and voice transmission as it offered better voice quality compared to the PSTN.

But, given the benefits of VoIP such as increased security and lower costs, ISDN is no longer as impressive an option as it once was.

As the ISDN will also be switched off in 2027, anyone still relying on the technology will need to upgrade to a digital phone line soon.

PSTN switch off timeline

Here are the key dates for the PSTN and ISDN switch off:

• November 2017 — It was first announced by the telecoms industry that the PSTN and ISDN lines would be retired in 2025. The switch-off date has since been pushed back to 2027.
• September 2023 — The ‘stop sell’ covered the entire UK, ceasing all sales of PSTN services. This means it’s no longer possible to purchase a PSTN or ISDN phone line, or even make changes to an existing connection.
• December 31, 2025 — Businesses are encouraged to switch to digital well ahead of 2027 to avoid connectivity issues.
• January 31, 2027 — This is the target date for complete withdrawal of all PSTN and ISDN services from the UK.

What is replacing the PSTN?

VoIP is the main technology replacing the PSTN for voice calls. It allows calls to be transmitted over the internet, removing the need for traditional copper wires.

It’s likely you already use the technology in some form, whether at home or in the office. For example, WhatsApp, Microsoft Teams and Google Hangouts are all popular VoIP services.

As hosted VoIP solutions offer a better service to traditional landlines for a cheaper cost, they are among the best PSTN alternatives.