Per a discussion on Gnucash-users, I propose adding a new chapter to the Tutorial to cover Expense Accounts. This chapter would be inserted as a new Chapter 6, to follow the chapter on Checking Accounts, and preceding the chapter on Credit Cards. Below is an initial draft for this chapter. Note that there are several gaps toward the end.

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Chapter 6. Expense Accounts

6.1. Concepts
An expense type account is used to allow you to track how much you spend on specific expenses. Technically, expense accounts are not a part of traditional accounting, but have become common with the increased capabilities of computer-based accounting systems.
Many people’s first experience with tracking expenses comes from Quicken(tm), where transactions can be assigned to categories. In Gnucash, these categories are set up as individual accounts, which allows Gnucash to apply the rules of double-entry accounting consistently.
Expense accounts can be as detailed or as general as you need. Some users need only a few accounts for personal  expense tracking. Others use Gnucash expense accounts to manage their expenses in great detail. The level of detail you choose is up to you. Keep in mind that with Gnucash, you can change accounts for transactions, so if your needs change later on, it is possible to move transactions around.

6.2. Setting Up Accounts

6.2.1. Simple Setup
For many users, the easiest way to set up expense accounts is to check the “Common Accounts” when you create a new Account Hierarchy. This will establish many of the most common expense accounts that users need. See “New Account Hierarchy Setup” in Chapter 3 of the Help guide for more information.

6.2.2. Complete Setup
If you have different expense accounting needs, you can refer to Chapter 3 of this manual, or Chapter 5.4 in the Help manual for instructions on how to create accounts.
Typical reasons for adding new or different expense accounts include: to track expenses for particular business purposes (e.g., specific types of supply expenses), to track expenses for particular tax purposes (e.g., tax expenses that must be reported to others), or simply to track expenses that are meaningful to you (e.g., payments made to a particular charity).

6.3. Entering Expense Transactions
While it is possible to enter transactions directly into expense accounts, it is not normally how these are entered.
For most people, transactions for an expense account are added when the user is entering data into the other account in the transaction. In other words, if you have an expense account for Charitable Donations (e.g., Expenses:Charity), you will typically add a transaction to the expense account by assigning a check in your checking account register to the Charity account.
If you open an expense account, you will see a register similar to most others you find in Gnucash. The informal column headings are slightly different, however. See the figure below for an example of an expense account register.

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6.4. Other Considerations for Expense Accounts
Because expense accounts are generated entirely by you, there are no statements against which you would reconcile your data. Therefore, there is technically nothing to reconcile. You can, of course use the reconcile process for expense accounts, which will lock the transactions for future editing.
One point to consider is that as your use of Gnucash continues, the balances in these accounts will grow, since there are usually very few credit transactions that reduce the balances. There is nothing wrong with this situation, but some users may wish to clear the balances in their expense accounts periodically. Zeroing transactions can periodically be entered that transfer the balance of the account to an Equity account. Gnucash includes a Closing Books procedure that includes zeroing out expense accounts. Keep in mind that this is not necessary, and that if you need to gather information on a given expense account, you can use various reports to extract that data without zeroing the account out.

6.5. Putting It All Together
6.5.1. Open GnuCash file
6.5.2. Purchases
6.5.3. Refunds
6.5.3. Reports