If you're filing a self-assessment tax form before 31 January deadline, watch out for websites that'll charge you up to £1,000 when you can do it yourself for free.

MoneySavingExpert.com has seen a number of reports via email and on our forum from users who've been stung by copycat sites, which charge huge sums to handle self-assessment tax returns (see our Self-Assessment Q&A for details on who needs to file a return).

One such website, Tax Return Gateway, demands a fee of between £150-£1,000 for a 'tax return submission service', even though you can do it free of charge via the official HM Revenue & Customs (HMRC) website.

MoneySavers say they've mistaken Tax Retun Gateway for the official HMRC site because it uses similar colours and key words. These sites also catch taxpayers out by paying search engines to have their websites appear at the top of search results, according to HMRC.

But these incidents aren't limited to tax returns. Other websites offer similar paid-for 'checking' services when applying for provisional driving licenses, European Health Insurance Cards, London's congestion charge and Esta forms, which are required when travelling to the United States (see the Boris Johnson aide stung by Esta copycat site MSE News story).

'HMRC knew nothing about the payment'

Forum user prezzaacc wrote: "We have just submitted a tax return online to a website called Tax Return Gateway.

"It's my first time [filing a tax return]... I have just learned this is not HMRC! It's a third party that checks my details and then submits them to HMRC and charges a fee for the service. Estimated at £150 but up to £1,000!"

Similarly forum user NickYCFC, who paid for £450 to Tax Return Gateway, wrote: "I entered its website in error as a first time online tax returner thinking it was the HMRC site.

"I was duped by the word 'Gateway', which I had keyed into the search engine.

"I then entered all my details, still unaware I wasn't in the HMRC site. At the end, the site predicted I would owe £438 in tax and asked me for a payment of £450, without which it would not accept my return. I checked with my chartered accountant wife and decided it was reasonable for HMRC to request the payment, and submitted the money.

"Four days later, I got post through from HMRC telling me I was owed £600 in tax, so I called it to find out if that included the £450 I had already paid. Obviously, it knew nothing about it, so I went back to retrace my steps and found my error."

Are firms allowed to do this?

The Office of Fair Trading (OFT) says it is not unlawful for firms to provide and charge for reviewing and forwarding services. However, businesses do have to make it clear that they're not affiliated to the Government, and that consumers will have to pay for a service which they could obtain from the Government for free.

The Tax Return Gateway homepage, for example, does say it isn't affiliated to HMRC. It also states, albeit in a smaller print, that taxpayers can file their return for free directly via the Government.

HMRC says it's concerned about copycat websites, but says it can't ask for them to be closed down if they're not using its official logo.

But Jamie Wyatt, technical director at Who4 Limited, which operates Tax Return Gateway, says: "We provide value and a quality service which is evidenced by the majority of happy customers.

"We are not breaking the law, therefore [the site is] legal, lawful and allowed."

I've been caught out. Can I get my money back?

In short, it's very difficult to get a refund. HMRC says many of these sites ask people to sign up to complicated, binding agreements, which are very difficult to get out of. Most forum users report these companies have been reluctant to hand back payments.

However, if you believe you've been misled or the website didn't make it clear it was a paid service, and you want to cancel your contract and get a refund, it's worth directly contacting the firm in question to ask.

You can also report the incident to the OFT or Trading Standards by calling the Citizens Advice consumer service on 0845 404 0506.

How do I file my tax return for free?

If you want to file a tax return for free, go directly to the official HMRC website – http://www.hmrc.gov.uk/ – and avoid using search engines, which can throw up different results.

If you've filed a self-assessment return with HMRC before, you can use the same log-in details to complete a form for the 2012/13 financial year before the 31 January deadline.

If you haven't got any existing log-in details, HMRC says TODAY is the last day you can apply to have these sent in time for the 31 January deadline.

For a full Q&A on who needs to file a return and what you must pay, see the Self-assessment Q&A: Fill in tax return now or face fines MSE News story.