Differences in the various pension protections available to savers against changes to the lifetime allowance (LTA) could leave almost a thousand investors worse off, AJ Bell said.
People with 'primary' protection against cuts to the LTA who do not have protection of their tax free lump sum could be £75,000 worse off than those with fixed protection, according to the SIPP provider.
AJ Bell obtained the figures in a Freedom of Information (FOI) request from Her Majesty's Revenue and Customs (HMRC).
The firm is now calling on HMRC to allow people with primary protection to apply for fixed protection, which the Revenue currently bars.
At A-Day, people with pension funds already worth £1.5m could apply for primary protection from punitive tax charges on investment growth of the fund.
People with fixed protection will still be able to take 25% of any pension fund up to £1.8m.
However, those with only primary protection and no lump sum protection will only be allowed to take 25% of the new LTA, £1.5m, when this comes into effect on 6 April 2012.
This means people with fixed protection can withdraw up to £450,000, but those with primary protection can only withdraw £375,000.
HMRC figures show there are 3,913 people who hold primary protection of their pension pots with no lump sum protection.
Of these, 935 had funds worth between £1.5m and £1.8m at A-Day and so could be hit by the sudden drop in LTA and tax free lump sum limits.
First mentioned in Cridland Report
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