The best time to convert is at the end of an accounting period. That way, you won't have to do a lot of extra work adding transactions that already occurred during a period. For example, if you decide to computerize your accounting system on March 15, you'd have to add all the transactions that occurred between March 1 and March 15 into your new system. It's just easier to wait until April 1 to get started even if you buy the software on March 15. While you can convert to a computerized accounting system at the end of a month, your best time to do it is at the end of a calendar or fiscal year. Otherwise, you have to input data for all the months of the year that have passed.
Whenever you decide to start your computerized bookkeeping, use the data from your trial balance that you used to close the books at the end of most recent accounting period. In the computerized system, enter the balances for each of the accounts in your trial balance. Asset, liability, and equity accounts should have carry-over balances, but Income and Expense accounts should have zero balances.
Of course, if you're starting a new business, you won't have a previous trial balance. Then you just enter any balances you might have in your cash accounts, any assets your business may own as it starts up, and any liabilities that your business may already owe relating to startup expenses. You also add any