Follow these steps to create a Credit Memo:
Google Checkout
There is an exception to this rule though. If you're offering Google Checkout as the payment method, you'll be able to refund the amount automatically. In that particular case, the button will be named as Refund instead of Refund Offline. More information about Google Checkout integration can be found here: http://www.magentocommerce.com/wiki/welcome_to_the_magento_user_s_guide/chapter_4#google_checkout.
Note that now your Credit Memo is final, the status of the sales order is changed to Complete.
That's a really good question. Magento offers no functionality besides the Credit Memo in the Community version. Sometimes it would be handy to register what your received, or to ask your customers to enter an RMA (Return Merchandise Authorization) before sending anything back. In the Magento Enterprise version, there is some functionality available to better support this process now. Community users should look for extensions if they want to have more features than available by default. There are multiple possibilities here; AheadWorks, one of the largest Magento extension providers, offers a good one at a reasonable price at: http://ecommerce.aheadworks.com/magento-extensions/rma.html.
For a lot of companies the functionality that Magento offers will not be enough to run all their processes. For instance, bookkeeping; this is something that Magento obviously doesn't offer. Magento is an e-commerce solution and not more than that. If you feel the need to integrate Magento with other software solutions then don't worry. First of all there are basic export possibilities available in Magento itself. You can find them in the menu by navigating to System | Import/Export. This offers already a lot of functionality that you can use to export data from Magento to third-party solutions and vice versa. You can do a lot with these functions, but unfortunately exporting orders or invoices isn't one of the offered functions. It can only be used for customers and products.
So, if you need to interface orders and/or invoices with other software solutions you'll need to use extensions or sometimes even custom software development. There are often extensions available for widely used standard solutions. Even if your bookkeeping software is developed by a local company there are still chances that someone has already developed an integration tool for it. However, even if an extension is available for your situation, we still recommend that you discuss this topic with a Magento partner or an experienced developer. Integrating different pieces of software is always more difficult and time consuming than you would think. And you cannot afford to miss orders or create errors in your bookkeeping software because the integration isn't working completely correct! Looking for a Magento partner to help you? Search for one using the search engines in your area or start here: http://www.magentocommerce.com/partners/.
Do not forget to ask for references and really check them! Preferably check references of companies that are close to your own business. In case of integration projects ask for a proven track record. Experience in this area has proven to be really important.