Hi Adrian - CB is flexible enough to bring in the numbers in any way that suits you and/or your accountant, so if moving over part way through the year I'd suggest you have two choices:
- export X month's transactions from Wave in CSV (I think you do this from the backup feature) then edit them so that they can be imported into CB. Typically CB imports sales invoices, supplier bills and bank transactions with the latter capable of being refined to just show receipts or payments to set against invoices or bills. In other words you import X month's sales invoices then import just bank receipts that pay off invoices and, by giving each a sales invoice reference, it automatically sets the money against the invoices. This saves having to manually match each receipt from the bank import.
As you indicate, in this way, when your accountant comes to look at the year's figures s/he only has one place to go to break down the numbers.
- Enter just X month's balances into CB using the "getting started" feature (or export a trial balance (TB) at the switchover date, from Wave (again in the backup I think) and import that into CB, as a Journal entry). In other words, whether it be sales, motor expenses or the bank balance, just the totals at the switchover date will be shown in CB.
So when your accountant comes to look at the year's figures, they will still have a full year's worth but if they had any query over what happened in the first X months, they'd still have to interrogate Wave (or the backup CSVs).
I didn't mention the 3rd choice of having X months in one system and Y months in the other as your accountant would be forced to interrogate both to extract the TBs and join them together, something bound to add to cost and frustration.
An unknown at this stage is the opening TB on Wave at 1 October. Hopefully this is installed in Wave so there's no need to worry about it but I know some accountants just keep this to themselves then add just the transaction totals from a client's books for the year. This should be a thing of the past with Cloud accounting as the accountant should be given full access to make sure the books reflect the accounts submitted on the tax return each year.
You should ask your accountant what they prefer, especially as they will know about your books and so be better able to advise. If it were me though I'd far prefer one place to go to look at a year's figures (eg option 1) and this would certainly be the case if HMRC decide that want to have a look at the accounts for that year.
There are a couple of videos that might help:
Basic setup of CB (before numbers): https://youtu.be/Y0kZ-fJKTNE
Opening balances: https://youtu.be/_DIraRMxq3M
Come back if any other queries but, once you sign up to CB, you have free support either via "tickets" or phone.