Corporation Tax Payment

Last month we paid our corporation tax as usual. It appears in the bank record in Clearabooks and on our bank statement. I am currently trying to reconcile last month's bank statement but Clearrbooks will not allow me to reconcile this transaction. I check the box then click "reconcile" but it shows the reconciliation report with the payment still unreconciled. I have done it three times now but the result is the same. Am I missing something obvious here?