This can happen if the product or service you’re selling is linked to an account that's not classified as an income-type account, sw1222.

QuickBooks Online will automatically record the transaction in your financial reports based on the account designated in the Income account field during the initial setup of each item.

I’ll guide you through the steps to review the setup and ensure that payments are correctly allocated to the appropriate account.

Here's what you need to do:

1. Go to the Gear icon and select Products and services.
2. Look for an item that is used in the invoices, then click Edit.
3. Scroll down a little bit and look for the Income account.
4. Click the drop-down list beside it and change it to an income account.
5. Click Save and close.

If the account is already classified as an income-type account, please ensure that it is not incorrectly labeled as Accounts Receivable. If the name is incorrect, rename it or make the necessary adjustments.

After that, go back to the Profit and Loss report and check if the transactions are now posted under the correct income account.

Additionally, I’d like to share these articles for further guidance on running Profit and Loss reports in QBO:

• Find the missing income and expense transactions in your Profit and Loss report
• Unapplied cash payment income on your profit and loss

Don’t hesitate to visit the forum if you need additional assistance or have follow-up questions about running reports or receiving payments from your customers. We’re here to support you in making the most of your QuickBooks experience.

@sw1222 

The response provided by @jenop2 is nonsense.  As a QB employee, they should know that QB won't allow you to assign A/R to a product or service  

To confirm, you're not seeing A/R on your P&L, you're seeing it as the split account on an item of income, correct?  If so, that's normal.  Even though you're on cash basis, when you receive a payment on an invoice, A/R is reduced in QB and shows it as the split account.