The customer invoice was paid on mar 6th, but it is not showing in unpaid invoice report dated february 28th?

I appreciate you here in the Community forum, @Cahir20. An invoice won't show up in your Open Invoices Report in QuickBooks Online (QBO) if it has been marked as paid. I'll provide more details below.

An Open Invoices Report lists invoices with outstanding balances, aiding in accounts receivable management and payment follow-ups. When a payment is recorded, the invoice status updates to paid in the database, removing it from the list of unpaid invoices.

Additionally, you can use this article to create personalised and professional-looking invoices, quotes, and sales receipts: Customise invoices, quotes, and sales receipts in QuickBooks Online.

Furthermore, this article can be your guide when you file your VAT return and record your VAT payment in QuickBooks Online: File your VAT return and record VAT payments in QuickBooks Online.

Please feel free to drop your Reply, if you need further assistance regarding your invoices. The Community team will also be actively responding to your queries through this thread. Take care.