Changes to Freeview's signals began in Scotland in 2017 and will continue across the UK until 2020.
The most recent changes took place this week across southwest Scotland, Tyne and Wear and County Durham, and Cumbria.
The changes are being made following a decision by Government, which requires some airwaves used by Freeview to be reallocated to allow for the future development of new mobile broadband services.
Transmitters across the UK are also being updated as part of a major engineering programme.
How will I know if I need to retune?
When changes to Freeview signals are taking place in your area, on-screen messages should appear to let you know.
If you haven't received any such messages but still want to check on the status of your area, you can also use Freeview's retune checker at freeview.co.uk/help/tv-changes.
Other terrestrial-based TV services that use Freeview channels such as YouView, BT TV, TalkTalk, EE and NOW TV will also be affected.
How do I retune?
Most equipment (especially more modern television sets) will retune automatically, but if at any point you find you are missing channels, you may need to retune your TV or set-top box manually.
The sheer breadth of TVs available means that there is no set way of doing this, and the method of retuning your set will very depending on factors like make and model number.
Most equipment will be simple to retune by pressing the 'Menu' button on your remote control, and navigating to a Setup menu or similar. From there you should be given the option to retune.
The advice Freeview themselves give is as follows:
Press menu on your box or TV remote control.
Now select set-up, installation, update or similar option. If you’re asked for a password the default code is usually 1234 or 0000.
Now select the first time installation option (sometimes called factory reset, full retune or default settings). Press OK if your equipment asks if it is OK to delete existing channels. This will clear your existing settings and find the new channel line-up. If prompted then save the channels that are found.
If you're still stuck and have the instructions for your TV handy, check them. They will provide you guidance on how to retune your set.
If you no longer have the instructions to hand, then fear not: the Freeview Advice Line is on standby to help, and can be contacted on Freephone 0808 100 0288.
Frequently Asked Questions on the matter can also be found in the FAQ section at freeview.co.uk/help/tv-changes.