Kettle Descalers :

Use tap water and your Kettle will suffer from limescale build up unless you descale regularly this will affect the performance of and lifetime of your kettle. Limescale buildup causes leaks, crackling, seal damage and if built up on the rim stops the lid from closing properly.

To descale: Every 2 months fill your kettle with  ½ white vinegar &  ½ water,   leave it to soak for an hour then rinse out a few times then boil with fresh water a couple of times before reusing.
Or
Mix 30g of lemon juice with 500ml of water, pour into the kettle and boil when cool empty and rinse.

If you have minor limescale you can cut a lemon into quarters and pop it in a kettle full of water then boil it a couple of times, wait until it cools then empty and rinse.
In all cases, if there is any limescale left you can use a little bicarbonate of soda on a cloth and wipe it off.
Only do this with a cool kettle and make sure your electric kettle is unplugged.
Or you can choose one of these simple and cheap kettle descaling solutions.