The holidays are over, September's here, it's back to reality (if you ever left it), so I wanted to go back to basics. A check-up if you like, to see if you could save yourself £1,000s. So no apology to MoneySaving aficionados - hopefully you'll pass with flying colours - as it's always worth a check, especially if you're one of those who reads this email, yet doesn't always act...

Q1. Are there more or the same number of bedrooms in your home as people?

If yes - it's likely you could save by switching to a free water meter (not for Scotland or NI), so use this water switching calculator at speed to see if you could save. The benefit can be much bigger than you'd think, as Steve emailed: "Since I've been reading MSE, we've had a water meter installed. Instead of £58/mth we now pay £22/mth." That's a saving of over £400/year.

Why the bedrooms vs people question? Water bills are based on your home's 'rateable value', which is roughly akin to how much it's worth; and bedrooms are a good indicator of that. Whereas water meters measure usage, which correlates roughly with the number of people. So if you've a big house with few people, meters usually win.

For more help including what to do if you're refused a meter, how to get water-saving freebies, and all rights, see our water-saving guide.

Q2. Have you switched energy tariff in the last year?

If not, you're almost certainly paying MASSIVELY over the odds, as it's likely you're on your provider's standard tariff (even if you were on a cheap deal, once it ends you're moved to this). And for someone on typical bills that's likely to be £300/yr over the odds.

Normally we'd tell you to compare and switch, but the MSE Big Switch Event starts next week and it's very likely to undercut the market's cheapest. The rules say you must pre-register, so the most important thing to do is check you're registered for MSE Big Switch 5 before Monday.

PS: Even some of those who have switched in the last year may well be able to save a decent chunk.

Q3. Do you pay over £50/yr credit card interest?

If so, STOP - you need to cut the rate. You may be wondering "why £50/yr?" Well, normally I focus on perfect solutions; today I'm focusing on easy. If you're only occasionally charged interest, you may decide it isn't too bad, but anything over £50 really is a clarion call for action.

The solution is usually to stop borrowing and shift debt to a 0% balance transfer card. These pay off credit and store cards for you, so you owe them instead, but with no interest. Always use our free Balance Transfer Eligibility Calc, which tells you which deals you're most likely to get.

The longest 0% deals available now include Halifax (eligibility calc / apply*), which is 'up to' 41mths for a one-off fee of 3.48% of the amount you transfer, and Virgin (eligibility calc / apply*), which is the same length, but has a higher 4% (min £3) fee. But unlike Halifax it isn't 'up to', so if you're accepted you'll definitely get the 41mths.

If you can repay quicker, Barclaycard (eligibility calc / apply*) is 'up to' 32mths 0%, with just a 0.68% fee and a possible £20 cashback. Or if you can repay even quicker, Halifax (eligibility calc / apply*) is 'up to' 25mths 0% with NO FEE. Tesco (eligibility calc / apply*) has no fee, and while it's a shorter 24mths 0%, it isn't 'up to', so if accepted you'll get 24mths.

Yet it's not just getting the right card, it's how you use it. Here are my golden rules:

a) Repay at least the set monthly min, or you can lose special rates.
b) Always clear the card/shift again before the 0% ends, or rates jump to the rep APRs - 20.9% (Virgin), 18.9% (Barclaycard & Halifax), and 20.6% (Tesco).
c) Don't spend/withdraw cash on them - it's rarely at the cheap rate.
d) You usually must do the balance transfer within 60/90 days to get 0%.

Far more help in Best Balance Transfers (APR examples). Also consider paying off debts with savings.

Q4. Can you name all regular payments you make each month?

If you're scratching your head then you need to check - you may be shocked what you don't know or have forgotten about. Don't assume this is a trite exercise: just by checking many are taken aback by what they find, such as Becky:

"I moved 2 years ago, but was still paying a direct debit to my old gym (£330/yr) and local wildlife centre (£43/yr) - both now too far away."

It's easy to check whether you've got direct debits or standing orders, as they're listed. Recurring payments (those made via giving the long card number) are trickier. For full help see our How to check your regular payments guide, and let me know what strays you find.

Q5. Do you just renew your broadband, phone, digital TV and breakdown deal?

You've guessed it - again, a 'yes' ain't good. Most providers don't reward loyalty, they charge for it. Each year bills go up for existing customers while firms fight for new customers with hard discounting. Yet there's a way of turning this around - haggling.

Simply call up (don't worry if you're shy, this isn't about being nasty) and ask for a better deal or say you'll take your custom elsewhere. The result can be huge. Rhys followed our tips: "Sky bill increased to £92/mth. I called and got 50% off, plus an HD discount & £50 credit - £600+/yr saved." For help, see our full haggling tips for Sky, AA and more.

Q6. Is your tax code 1100L?

If it is, you're on the standard tax code most people get - fine for most but if you've any unusual circumstances, it's likely to be wrong. If it isn't, HMRC thinks you've unusual circumstances, so you should check. If you don't know what your tax code is, find out.

To check, use our Tax Code Calculator. It'll help explain whether your code is likely to be correct for your earnings and situation. And don't assume your tax code is right: each year MILLIONS are wrong, and that may mean you're due cash. As Alice tweeted: "@MartinSLewis Checked tax code thanks to you, and error means I'm now owed £2k."

The 'Are You Wasting Money?' Quiz
Check your tax code to see if you're being clobbered for more than you owe

Q7. Did you auto-renew car insurance the last time it came through?

If you did, it's likely you've paid higher rates for your loyalty. Insurers usually offer the best deals to new customers, giving existing ones higher rates in the hope they're not challenged. And with prices rising rapidly - up 17% over the past 12 months - it's not too late to check now, even if you're not at renewal.

a) Check for cheaper.
Our full Cheap Car Insurance guide shows how, but briefly: i) Combine comparison sites for a wide search - our current order's*, Gocompare*, CTM and MoneySup*. ii) Check competitive insurers that comparison sites miss, including Direct Line* and Aviva*.

b) Changing policy midway through.
If you find a cheaper deal, provided you've not claimed, for a £50ish admin fee (factor that in) you can usually cancel your policy and get the rest of the year refunded. You won't earn this year's no-claims bonus, but if it means you save now and prevent future price rises, it can be a big winner. Full info: Switching mid-policy.

As Mubariz tweeted:"Just had my car insurance HALVED (£543 saving) plus £150 refund by changing mid-policy. HUGE thanks."

Q8. Is your mortgage rate over 3.5%?

Mortgage rates are at record lows with rates of 1%-2% widely available, yet millions of people are stuck paying over 3.5%, often on the lender's standard variable rate - these average 4.7%.

Of course, not everyone can switch. It depends on your credit score, how much equity you have in your home, affordability and more; but it's always worth checking. For every 1% point you lower the mortgage rate you save £80/mth per £100,000 owed. Here are three key pointers...

1. Benchmark your cheapest deal using our Mortgage Comparison Tool.
2. Use the Ultimate Mortgage Calculator to find what you'll save.
3. Read my free printed 60-page Remortgage Guide to hold your hand through it.

And as this post on my Facebook page shows, it can be big money: "Downloaded your remortgage guide and have managed to get a new deal saving £128/mth, saving us £3,000 over 2yrs."

Q9. Got a credit card and always repay it in full? Does it pay you?

Paying off in full means you don't pay interest. Bravo. Yet there's another step. When you use a credit card, the retailer has to pay the card firm a transaction fee. With a cashback card you effectively get this put in your pocket. As Anna tweeted me: "@MartinSLewis Glad I read about Amex cashback card: I'll get over £200 paid."

The fee-free Amex Everyday (eligibility calc / apply*) pays 5% cashback (max £100) for the first 3mths, then tiered rates up to 1% after that, or if you spend more the Amex Platinum can pay a touch more. The best-paying fee-free non-Amex, so it tends to be more usable, is the Aqua Reward (eligibility calc / apply*) which pays 0.5% on all spending.

But only do this if you'll set up a direct debit to repay IN FULL each month, or you'll pay 22.9% or 19.9% rep APR interest, which more than wipes the cashback gain. Full options in Top Cashback Credit Cards.

Q10. Are you paying more than £10/mth for your mobile?

If so, ask yourself why. If you're paying a hefty whack because you're still paying off your handset or roam abroad, that's one thing. But if the cost is just from calls or data use, £10 is over the odds for some.

The reason I set this figure is because you can get a virtually 'all-you-can-eat' Sim-only tariff for £9/mth from Three* - here you get a year's unltd mins/texts & 4GB 4G data (without free roaming). If you need more data, from 9am today (Wed) EE's flogging 8GB for £20/mth but you get a £75 Amazon vch & 6mths' Apple Music too.

So stop ringing up big bills. Full info & low-use options in Sim-only deals.

This article first appeared in the weekly email on 7 September 2016 and was updated on 13 September 2016.

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