Government-owned National Savings & Investments (NS&I) has admitted thousands of savers did not receive interest due at the start of this month.
The bank blames "technical issues" and says the cash will be paid as soon as possible but has not stated a precise date.
Approximately 8,000 people who took out an NS&I Income Bond between 24 and 28 November did not receive their interest due on 5 January.
The account currently pays between 1.71% or 2.02% before tax, which is easily beatable. As it offers easy access, you can withdraw the cash at any time.
You could earn up to 3.35% elsewhere with easy access or 4.7% if you're prepared to lock your money away for up to three years (see the Top Savings guide).
Steve Owen, from NS&I, says: "We know that the delay in income payments will be an inconvenience to our customers and we apologise profusely for this.
"We are working to rectify the problem, and hope to be able to make January's income payments as soon as possible. We will provide a further update once we have the date of payment confirmed."
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