Cash Isas are much simpler than they sound, but there are a few things you need to know before you start comparing them.
Do you enjoy paying tax? No, of course you don't. So it makes sense to use an individual savings account (Isa), which comes with one incredible perk - the taxman can't touch it. The interest you earn on your money is yours, and yours alone.
You'll want to switch occasionally in order to find the best deals, probably at least once a year if you're using an account with a 12-month bonus
Felicity Hannah, financial journalist
Each year you have an Isa allowance, which is an amount you can save into a tax-free account.
That amount resets every new tax year and, if you haven't used it, you lose it.
You can save the allowance amount into a cash Isa and/or a stocks and shares Isa without troubling the taxman.
Your allowance rises each year, but for the 2013-14 tax year it's a maximum of £11,520. A maximum of £5,760 of that can be saved into a cash Isa, or you can save as much of the allowance as you like into a stocks and shares Isa.
The tax year runs from 6 April to 5 April the following year. In 2014-15 the Isa allowance will be £11,880, of which a maximum of £5,940 can be put into a cash ISA.
Unless you're a higher-rate taxpayer, you may not have realised that you pay tax on any interest you earn.
That's because it's deducted before you receive it. The bank or building society automatically siphons off 20% of your interest and passes it along to the taxman.
Higher- and top-rate taxpayers have to declare their earnings to the taxman so that they can pay the extra tax.
But all taxpayers can avoid this by saving into a cash Isa.
There are as many kinds as there are standard savings accounts. You can get regular-saver Isas, fixed-rate bond Isas and easy-access Isas.
In fact, the only difference between a cash Isa and a normal savings account is that the taxman won't take a cut of the interest you earn.
That means you can save in the best way for you. If you haven't put any money aside this tax year then it makes sense to start by using your tax-free allowance.
These tax-free accounts are only available to UK residents aged 16 and over. If you're under 16 or want to save for a child, then take a look at junior Isas.
Maximising the return on spare cash is important - and taking advantage of tax-free interest is a great place to start
Most people use their Isa allowance to make long-term savings. Once you've invested money into an Isa, the taxman can't touch the returns until you withdraw it.
But even if you just want somewhere to keep your rainy-day fund, an easy-access cash Isa could be right for you.
After all, if you're lucky then you'll never need to touch your emergency cash, so you may as well keep it in a tax-free account.
You can switch cash Isas to find a better rate, you just need to transfer the money. If you withdraw it then it stops being tax free and you can't reinvest it.
Your current Isa provider is obliged to let you transfer money out of its account and into a better one, so don't let them put you off.
Often, your new Isa account provider will take care of this for you and will ask if you are transferring funds in when you open the account.
Having said that, not all providers accept transfers into new accounts, so you need to check that before opening a new account.
When you compare cash Isas through Gocompare.com, you can clearly see whether an account allows transfers. That should make it easier to choose the best deal for you.
If you've locked your money up in a fixed-rate bond cash Isa, then you may have to pay a penalty in order to transfer the money into a new account.
Do the maths and make sure it's still worth it before going ahead.
Some accounts pay a bonus rate for the first year in order to tempt savers in. These can be a great way to earn a better rate.
But you should make a note of when you open the account and be ready to switch on the first anniversary.
If you're particularly savvy you can keep switching to a better account every year, comparing cash Isa rates to find the best each time.