Available in Sage 50 Premium Accounting and higher.

Change the Length of Your Company's Account Numbers

To change the length of your company's account numbers:

In the Home window, on the Setup menu, select Settings. Open General (Accounts), and select Numbering.
Select a Number of digits in account number from the list (up to 8).
Click OK.

Note: To shorten your account number length by one digit, your current account numbers must all end in zero. To shorten them by two digits, they must all end in two zeroes - and so on. Otherwise you need to remove some accounts or ask your accountant to re-number them.