A self-employed artist told a court she thought £500 paid to an alleged scam website would come off her income tax bill.
Sharon Walford, who also runs a charity, said she used the taxreturngateway website to fill in her tax return thinking it was the official Her Majesty's Revenue and Customs (HMRC) website.
The four men who ran taxreturngateway, Richard Hough, Michael Hughes, Jamie Wyatt, and Stephen Oliver, are alleged to have made more than £5million in five months from it.
Hundreds of users made similar complaints to Mrs Walford, saying they were misled into believing they were dealing directly with HMRC, Teesside Crown Court heard.
Users thought fees of between £150 and £1,000 paid to the site would come off their tax bill, but the money was kept by the site as fees.
"I had done my tax return online for about six or seven years," Mrs Walford told the jury.
"Each time I used the HMRC site after typing 'self-assessment tax return' into the internet search engine.
"I did the same thing in January, 2014, but that time I logged on to what I now know to be taxreturngateway.
"At the time I thought I was dealing with the official HMRC site as I had done in previous years.
"The taxreturngateway page was the same as HMRC, logos, colours, everything really.
"There was a message which said 'we will submit your return but not check it' which I thought was unusual.
"But I wouldn't have used the site had I not believed it was the official HMRC one."
The jury was shown images of a sequence of pages from the taxreturngateway site asking users to fill in their income and other financial details.
"All the pages looked the same as the previous year when I was on the HMRC site." said Mrs Walford.
"At the end the site asked me for £500, which I paid.
"I hadn't been asked for money in previous years when submitting the return, but I just thought the £500 would come off my tax bill when I got it.
"When my bill arrived two days later, the £500 had not been deducted."
Mrs Walford phoned HMRC to ask why.
"They said they knew nothing about my £500," said Mrs Walford.
"They said submitting a tax return online was free, and I should contact Trading Standards about what had happened.
"As far as I was concerned taxreturngateway was a con, I felt robbed of my money."
The court heard Mrs Walford wrote several letters of complaint to taxreturngateway, and phoned numbers for the company she found online.
She was eventually given a full refund by taxreturngateway.
Under cross-examination from Graham Trembath QC, defending Oliver, Mrs Walford conceded she must have ticked a box which said: "I grant permission to taxreturngateway to act on my behalf."
"Surely that makes it plain taxreturngateway was not HMRC?" Mr Trembath asked Mrs Walford.
Mrs Walford said at that point in the process she had already made the assumption she was dealing with the official HMRC site.
Beverley Linfoot told the jury she used taxreturngateway over a few days to fill in a tax return on behalf of her husband.
"It asked me to pay £280," she said. "That had not happened when I'd previously used the HMRC website, but I just thought things had changed as so much does change on the internet.
"I assumed the money would be credited against my husband's tax bill, but when the bill arrived it had not been credited.
"I called HMRC to ask why, and they said I had not paid £280 to them.
"The lady felt sorry for me, but said I still owed the full amount.
"I was very annoyed with the taxreturngateway site."
The clourt heard Mrs Linfoot complained to the owners of the site who offered her a 50 percent refund, which she accepted.
Wyatt, 27, and Hughes, 26, both of Peartree Rise, Seaton, Seaham, Oliver, 47, of The Folly, West Boldon, and Hough, 43, of Thorpe Waterville, Kettering, Northants, each deny conspiracy to defraud between June, 2013, and June, 2014.
Wyatt, Hughes, and Oliver deny a second charge of conspiring to defraud by denying consumers the right to cancel under distance selling regulations.
The trial is in its third week, and is expected to take eight weeks.