I'm a travel agent. In 2020 I received a deposit for a canceled journey. I kept the money for a future trip. How can I record the payment that is not revenue for 2020?

I'm here to ensure that you're able to record a payment, mary73.

To record the customer prepayment, you’ll need to record a retainer or deposit. This way, the transaction will show correctly in your financial reports.

Let's go over and create liability account to track the amount of the retainer you received from your customer.

Here's how:

1. Click Settings ⚙, then hit Chart of Accounts.
2. Select New.
3. From the Account Type ▼ drop-down, choose Current liabilities.
4. From the Detail Type ▼ drop-down, Client Trust Accounts - Liabilities.
5. Enter a name for the account (ex. Trust Liabilities.
6. Select a Default Tax Code, enter an Unpaid balance, and an as of date.
7. Press Save and close.

Once done, you can now create a retainer item you can use to receive the deposit or retainer from your customer. See the steps below on how.
 

1. Hit Settings ⚙, then click Products and Services.
2. Choose New.
3. From the Product/Service information panel, select Service.
4. Enter a name for the new product or service item (ex. Retainer).
5. From the Income account ▼ drop-down, select Trust Liability Account.
6. Click Save and close.

You can check this article for additional information on how to record a retainer: Record a retainer or deposit.

Additionally, I've included this article that'll help you generate and manage reports for specific accounts or transactions: 
 

• Customize reports in QuickBooks Online.
• Memorize reports in QuickBooks Online.

Feel welcome to get back on this thread if you'll need assistance in dealing with accounts receivable. We're always here to help you.