Adding a prior bank account

My husband finally got a separate business checking and credit card back in March and also set up his quickbooks account at that time. I'm trying to do our tax info and was thinking it would be easier if I had all of his business transactions in one spot for the 2020 year. I know how imports work and could easily get a CSV file that only contains info from our personal account that he spend on the business in Jan and Feb 2020 but I guess I would still have to set up another banking account on here to add it to? I wouldnt want to confuse the banking numbers for his current accounts. Or should I link our personal so it auto-imports and then go through and exclude all non-business transactions? Has anyone ever done something similar or have any suggestions? Thanks!