In the expense tab. Why do some transactions show up twice as "check" and as "expense"?

 Let's investigate what's causing the expense transactions to show up twice in your account, charles35. 

Adding transactions instead of matching causes a duplicate entry if you already have created transactions in QuickBooks Online (QBO). We can pull up and review your expense transaction directly from your account register. This way, we can identify why they are showing as duplicates in the Expense tab. Let me show you how:

1. Go to Accounting on the left menu. 
2. Select Chart of Accounts.
3. Find your bank or credit card account.
4. Under ACTION, tap View register.
5. Review and open each of your expense transactions.

For more details about this one, see Find, review, and edit transactions in the account registers article. Once you have reviewed them and confirmed they are all in duplicate records, we can open and delete the duplicate transactions. Here's how: 

1. Go to the Expenses menu.
2. Find and open the transaction.
3. Review the transaction. Make sure you need to void or delete it.
4. If you want to include the void or delete date, add a note to the Memo or Message section.
5. Tick More in the footer.
6. Tap Void or Delete.

Feel free to visit our Expenses and vendors page for more insights about managing your expenses in QBO. 

I'd like to know how you get on after trying the steps, as I want to ensure this is resolved for you. Please reply to this post and I'll get back to you. Happy Holidays.