The company also reported one in five have so far made partial use of the increased allowance.
Research from the general investment platform showed that in the six months following the launch of the NISA over 62,000 investors have used the new £15,000 allowance.
There have been over 10,000 brand new investors to the platform putting in the full NISA allowance.

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Collectively there has been a 91% increase in the amount of money invested when compared to the same period in 2012 and 2013 combined.
However, while the initial flows have been strong, the research also indicates that over two thirds (70%) of investors are yet to take advantage of the new £15,000 allowance ahead of the financial year end.
Stephen Wynne-Jones, head of marketing operations at Cofunds, said: "Although there have so far been strong flows into NISAs, there are still plenty of investors yet to take advantage of the tax benefits. This is obviously where advisers come into play, liaising with their clients to raise awareness the changes and recommend they review their portfolios."
In terms of the flow of funds into NISAs, mixed investment 20-60% has been the most popular sector.
Mr Wynne-Jones said: "The mixed investment 20-60% sector has been a consistent leader for ISA funds, providing greater flexibility and a wider choice for investors.
"These funds offer a safer haven for those investors who act on the side of caution, whilst at the same time maintaining some exposure to rising markets.
"As the end of the financial year fast approaches, the first one since the NISA changes last year, we expect to see flows increase significantly as the new limits really come into their own."