More than half of technical queries made to SIPP operator Curtis Banks by advisers concerned the subject of death benefits rules.
The queries suggested that even though the rules can be flexible and tax-efficient, they can also be complex, the business said.
According to the self-invested personal pension (SIPP) operator, this has been an ongoing issue for advisers and is not a "one-off spike" in queries.
The questions asked covered a range of topics including; when beneficiaries' drawdown is available, minors inheriting death benefits, tax implications and lifetime allowance charges.
Curtis Banks said clients have requested further clarity on how they can use expressions of wish forms to pass on their wealth in a way they want to.
Ridgeways (FP) director Kevin Blake said death benefit rules are still overly complicated for advisers, some four years on since pension freedoms.
"It is very easy for them to do something or forget to do something, such as not amending their expression of wishes if a beneficiary dies before them, which then causes problems when distributing the benefits," he said.
Blake added: "Reform of this system is badly needed."
Curtis Banks pensions technical manager Jessica List said the number of queries they received on the subject of death benefit rules was "disproportionately high".
"It is such a key area now, with so much complication within the rules and variation between different providers, that advisers want to be confident that they've covered all bases in each individual case."
She added the current rules can be "extremely generous" for beneficiaries however, the level of complexity and consequences seem an "unnecessarily high cost" to pay.
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