You need to be on a transaction that is Paid By Check and has a check number on it before clicking the Print Check link. If you are not on a valid checking account transaction you'll get the following error -
If you don't have a customer in the Check Payee field, the Customer List will popup so you can pick a customer. If the customer is not yet in the Address Book it's best to add him before you do the Print Check. That will put him in the Check Payee field for the transaction.
Assuming you have a valid transaction and a check payee in the transaction you'll get the check form -
On this form its possible to edit the Check Payee, Name, Address, City, State, Zip, the Memo and the Customer Id Number. Changing the Customer ID will load a different check Payee into the top of the form.
Update: Will update any changes you made to the form and save them to the source record.
Print Ck: Will print the check to the printer.
Stop: Will exit this form without saving any changes or printing the check.
CHECK SETUP: BEFORE you try to print any checks print a check to a piece of paper and hold it up over your check forms to be sure it matches your checks. You can adjust the lines up/down and left/right in the check setup section under My Account. See My Account/User Preferences for details.
