Carry forward loss

Two accounting years ago (2016/17) a company I run had a trading profit (before tax) of:

£17,851.63

Based on this, the following was paid as corporation tax:

£3,540.37

The following year (2017/18) the same company had a trading loss (before tax) of:

£-18,078.67

I carried backwards the maximum amount of this loss (£17,851.63) which results in a tax repayment (to me) of £3,540.37. The remainder of £227.04 I wish to carry forward to the current year (2018/19).

I do not know how handle the carry backward and carry forward part of corporation tax.

Currently I have just added a journal entry that debits (2320) Corporation Tax with £3,615.80 and credits (8500) Corporation Tax Charge for the Year with the same figure. This figure is basically 20% of the total loss (before tax) for the year. Then when HMRC repaid me £3,540.37, I created a journal entry which debited the current account for that amount and credit the (2320) Corporation Tax by the same (the reason it was a journal entry, is because HMRC actually sent £24.05 extra, as interest, so I split this amount off and set it as (4900) Miscellaneous Income). My balance sheet for the end of the accounting year shows a corporation tax asset, which is the CT being carried forward.

I feel like my conversion of the full loss into a CT amount, claiming some of it back and bringing the remainder forward is likely wrong. Instead I feel like I should have just worked out the corporation tax on the maximum I could carry backwards (£17,851.63) and the remainder (£227.04) should have been somehow carried into the following years P&L, as some sort of carried loss.

Could anyone advise me the best way I can handle the above with quickfile?