How do enter income that was for previous year but did not recieved until current year?

Good day, simplitia.

Allow me to assist you in recording income received the following year.

Creating an invoice is ideal if you expect to be paid for the products and services you sell in the future. 

With that, you can create an invoice and record an invoice payment.

Here's how:

1. Click on + New.
2. Select Invoice.
3. From the Customer ▼ dropdown, pick a customer. Make sure all of their info is correct, especially their email address.
4. Review the Invoice date. Then from the Terms ▼ dropdown, select the due date. 
   Tip: Net refers to the number of days until the payment is due. The default is 30 days, but you can change the due date if needed.
5. From the Product/Service column, select a product or service. You can also select +Add new to create a new product or service right from the invoice.
6. Enter a Quantity, Rate and Amount if needed.
7. Select a VAT rate.
8. Once done, hit Save and close.

After that, you can record an invoice payment. Just make sure to include the same date as the invoice or within the same year. Use this link as a reference: Record invoice payments in QuickBooks Online.

I've also added this article as a future reference: Reconcile an account for multiple months or years of transactions and financial statements.

Feel free to post again in this thread if you have questions or other concerns about invoices and payments in QuickBooks Online. I'll be here to help. Keep safe!