Can I add old invoices that I have already been issued/paid by my clients from before I had Quickbooks so that my books show the entire year?

Joining the thread to share some more information about adding old paid invoices, @lorena-violetage.

Fiat Lux - ASIA's answer is correct. You can use both methods of adding invoices or recording them as sales receipts. Please be reminded that these are posting transactions an will affect your register balances.

For more information about these entries, I've added these links for you:

• What is the difference between an invoice, sales receipt, bill, and statement?
• Invoices vs sales receipts: which to use when

To add the transactions, go to the + New icon in QuickBooks and choose the transactions you want to record.

Please come back here if you require further guidance with recording sales transactions in QuickBooks. I'll be right here to help.