The amount invested in Innovative Finance ISAs (IFISAs) has increased but the number of account openings has fallen.
The latest HMRC data for the 2018/2019 tax year shows £328m was invested in IFISAs from 38,000 accounts.
This is up from £277m invested in the 2017/2018 tax year but there were 49,000 account openings during that year.
The figures take the total invested in IFISAs to £641m across 92,000 accounts.
The data shows the market value of IFISAs, which takes account of interest earned and cash on deposit, is £719m.
HMRC is still claiming the subscription figures are unreliable though due to a low level of data.
Providers have previously blamed this on the complicated submissions process.
A spokesperson for The Investing and Saving Alliance (TISA) said they were not sure why HMRC felt the subscription figures were unreliable but said the market value is close to its own data showing a value of £711m as of April 2019.
Its figures represent 25-30 per cent of the market, including the larger platforms.In contrast, the number subscribing to cash ISAs increased by 1.4m to 8.4m but the number subscribing to stocks and shares ISAs fell by 450,000 to 2.4m.
The amount put into cash ISAs rose from £36,689 to £43,966, while the amount subscribed into stocks and shares ISAs fell from £27.7m to £22.6m.
At the end of 2018/2019 the market value of cash and stocks and shares ISA holdings stood at £584bn, this was down four per cent annually.
Read more: IFISA inflows set to hit £1bn