It’s a no brainer for every first time buyer – from 1 December Help to Buy ISAs become available. Here when you save for a deposit the government adds 25% on top.

Nothing else comes close to this, so you want to get the maximum you can in there. Let me run through the foundations in 10 steps.

1. Every first-time buyer aged 16 or over can open one

To count, you must not have owned or part owned a residential property, in or out of the UK, whether bought or inherited.

2. It's an individual product – couples are treated separately

If you’re in a couple and are both first time buyers, you can get one each. If only one of you is a first time buyer, then you can still get one.

3. It can be used for any property type with any mortgage

It can be used on homes costing up to £250,000 or up to £450 within inner and outer London boroughs. It’ll work on any home mortgage (so not buy-to-let), including shared ownership and you won’t need to get a mortgage from the same firm your Help to Buy ISA’s with.

4. You can save tax-free up to £1,200 in the first month, then up £200 a month after that

If you've less, you can contribute less (if the provider's terms allow it) and it'll still work. Missing a month is fine, though you’ll still only be able to put in a maximum of £200 the next month.

If you want to save more, don’t worry, it doesn’t have to be the sole place you save for your deposit, you can use it in conjunction with other savings.

5. The state adds 25% tax-free to whatever’s in the ISA when you use it for a deposit

The 25% is only added at the point you use the ISA money as a deposit (it must be by 2030) and it’s added to everything in the ISA, including interest. To trigger the bonus, you need to have saved at least £1,600 (so you'd get £400 extra) and the biggest bonus it’ll give is £3,000 (so that’s on £12,000). If you have more, you can still save in the ISA, you just won't get more than £3,000.

In practical terms, you close down your Help to Buy ISA account, and your solicitor applies online for the bonus (they’re allowed to charge up to £60 for the admin).

6. Only one Help to Buy ISA per person is allowed, but you can transfer it to up the rate

Unlike cash ISAs, where you can open a new one each tax year, you're only allowed one Help to Buy ISA, but you can continue to add to it each tax year. Yet you can always transfer it to another provider if their interest rate drops.

7. You can't contribute to a Help to Buy ISA and a cash ISA in the same year

Though nothing stops you opening a Help to Buy ISA if you have cash ISAs from previous years, or a stocks and shares ISA from the same year.

Even though cash ISAs let you save more, getting a Help to Buy ISA wins, as no interest comes close to the Government’s 25% top-up.

It's worth noting the 'loss' of your cash ISA allowance’s mitigated somewhat from April 2016, as the new personal savings allowance means basic-rate taxpayers can earn £1,000 tax-free interest in all savings (£500 for higher-rate payers).

If you already have a cash ISA there are ways around this - see www.mse.me/helptobuyisa for full help on what to do.

8. If you decide not to buy a property – you can take the money out

You can take cash out of a Help to Buy ISA whenever you want – you just miss the bonus. It stays tax free and you get the interest.

And if you do need to withdraw some of the money, you can still carry on contributing afterwards, and will still get the bonus on what’s in there when you use it (depending on your provider’s rules).

9. It's worth doing even if you're buying imminently

The minimum amount you need to get a bonus is £1,600 (you would get £400). This takes ‘three months’ to put in, because you can deposit £1,200 in month one, then up to £200 each month after.

Yet it’s a calendar month, in practice you could hit this faster if the dates fall right. Eg, dunk in £1,200 on 31 Jan, then £200 in Feb, and £200 on 1 Mar and you’d be ready to go.

10. The best-paying Help to Buy ISAs

Even though the Government will pay the bonus, you still want to earn maximum interest as well, so choosing the right ISA is important. At the time of writing Barclays, Lloyds, Nationwide, NatWest, Santander and Virgin Money have committed to offering Help to Buy ISAs, but no rates are out.

Every time a new rate is published, I’ll be analysing the best buys and putting them at www.mse.me/helptobuyisa. My suspicion is rates will be decent as banks will use them to cross-sell you mortgages, and the amounts you can put in aren’t big, so they can afford to make rates high.

Get a free letter from Santa

If your kids write to Father Christmas, Santa's Grotto, Reindeerland, XM4 5HQ by 6 December, they should receive a personally addressed reply from Santa and his elves before Christmas Eve.

My Christmas predictions

Many stores’ Christmas marketing and promotions calendars are remarkably consistent from year to year. So I’ve studied back five years to predict what’ll come this year. So in the first week of December, a £50 Argos spend should get a £5 voucher. Then the following week, the big thing everyone is waiting for is the Boots half price Soap & Glory gift set. Plus on around 14 December I predict M&S will reduce its gifts, wraps and other Christmassy items – followed soon by other stores. So if you can hold for that, do. Check out my Xmas Deals Predictor at mse.me/predictor