Currently Kashflow does not let you make any additional adjustments to individual VAT returns.
A journal is not necessarily required as the accounts may already reflect any VAT correctly but this was not included in VAT returns. This is often the case for any fuel scale charges adjustments or for clients when they are switching to using Kashflow and preparing the first VAT return. A manual adjustment may be required to boxes on the return.
Sage currently has this function and it is extremely useful