A chartered accountant was charged £650 by an alleged scam tax return website when she was due a tax rebate of more than £1,600.
Gemma Parry-Jones told a jury she mistakenly logged on to the taxreturngateway site thinking it was the official Her Majesty's Revenue and Customs (HMRC) site.
Four men who ran the site from offices in Sunderland are alleged to have made more than £5million from it in five months.
Mrs Parry Jones told Teesside Crown Court she is a chartered accountant employed by Goldman Sachs investment bank in London.
"I have been doing my self-assessment tax return online since a year or two after I arrived in the UK in 1998," she said. "I always used the HMRC official site.
"In January of 2014 I wanted to do the return and I Googled 'self assessment tax return', or something like that.
"A list of search result came up on my laptop, and I think I clicked on the top one, or one that was near the top.
"What came up was a page with boxes to fill in, it all looked very similar to what I had seen in previous years."
Mrs Parry-Jones said her tax return was relatively simple: "I am PAYE. I do have a property, but other than that my return is not complicated.
"As a chartered accountant, I am well able to do it myself. There is no way I would want to pay anyone to do it.
"I completed the process on what I now know to be taxreturngateway, and it asked me for £650.
"That was odd to be asked for money at that stage, but I wanted to complete the return by the January deadline, and I know the revenue like you to pay first and deal with any adjustments later.
"I paid the £650, and it wasn't until I received an email and a text from taxreturngateway that I realised I had not been dealing with the official HMRC site."
Mrs Parry-Jones said she made several calls and sent several emails to taxreturngateway, but these went unanswered.
"I was also on the phone being held in a queue," Mrs Parry-Jones told the jury. In total, I think I was held in the queue for about seven hours.
"I kept on getting a recorded message telling me I was moving up the queue, but I didn't reach the top before I had to ring off."
Mrs Parry-Jones said she completed her tax return using the official HMRC website, and later received a rebate of more than £1,600 for that year.
The jury heard earlier hundreds of users made similar complaints to Mrs Parry-Jones, saying they were misled into believing they were dealing directly with HMRC.
Some users received refunds from taxreturngateway, before the site closed in the spring of 2014.
Lawyers for the four defendants said disclaimers on the website made it clear it was not the official HMRC site.
Jamie Wyatt, 27, of Peartree Rise, Seaton, Seaham, Michael Hughes, 26, formerly of Hutton Henry, now also of Peartree Rise, Stephen Oliver, 47, of The Folly, West Boldon, and Richard
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.