(Reuters) - A top U.S. banking regulator is set to propose that banks bolster recordkeeping requirements for accounts held by fintech companies on behalf of their customers, following the collapse of bank-fintech middleman Synapse Financial Technologies earlier this year, which led to the freezing of thousands of accounts.

Taken together, the new requirements would ensure consumers have timely access to their funds, even in the absence of a bank's failure, the Federal Deposit Insurance Corp said.

Under the FDIC's proposal, banks that work with fintech companies would need to identify the beneficial owners of each account and its balance. Third parties -- like Synapse -- would be allowed to maintain those records as long as certain requirements are met, such as a bank retaining unrestricted access to that data even in the event of a middleman's bankruptcy or insolvency.

Synapse filed for bankruptcy in April, leading to the freezing of accounts for customers of its partner banks, including Tennessee-based Evolve Bank & Trust, which in turn worked with fintech companies to offer banking services like deposit accounts.

The FDIC on Tuesday is also set to finalize a policy that would bring heightened scrutiny to bank mergers that would result in a combined bank with more than $100 billion in assets.

The new rule would update the agency's merger guidance for the first time in 16 years, and would put special emphasis on maintaining the stability of the banking sector, agency officials said when first proposing the rule in March.