Interest: Interest Review Unit (IRU): General principles: Filing online
When an objection involving an online filed return is looked at and the position is not clear, ask the Electronic Business Unit to find out whether the problem is the result of customer or agent error, system problem or HMRC error.
If the customer or agent has incorrectly sent information or not followed the correct online processes, then the interest charge should be upheld.
If HMRC is at fault consider giving up interest that has arisen because of the error or system problem. This will be limited to the interest arising on any extra tax shown to be due. The original amount of tax, shown to be due by the return, should have been paid and the error did not cause the delay in payment of that part of the tax.