Manual accounting is how all accounting was done in the past, on physical paper, handwritten. If you sold an item, you had to physically create a receipt with paper and pen and then physically record it into a ledger for your accounting. As times have changed and technology has developed, a lot of financial processes are digitized. When your business has a financial transaction, it is automatically recorded in your computer system, and then imported into your accounting software for tracking. That is computerized accounting.