It happens the way I explained for all my clients who pay corp tax before the due date which is 9 months and one day after their accounting period ends.
(I enter £10 on all clients CT600’s, so credits or refunds above that are paid out)
For example one clients Tax due was £15,241 year ended 31st Aug 2016
Tax was Paid early on 25th Oct 2016
Tax Due date was 1st June 2017
The client received the interest of £45.72 in their bank on 12th June 2017 just 11 days after the tax due date.
This is the HMRC’s records for this example: