Thanks for reaching out to us! QuickBooks Online will automatically follow the numbering once you've created an invoice. Let me show you how to enable custom transaction number and set your own numbering preferences for your invoice number.
Go to Settings ⚙ and select Account and settings.
Select Sales, then select anywhere within the Sales form content section.
Turn on Custom transaction numbers.
Select Save, then select Done.
Go to Get paid & pay and select Invoices.
Open an invoice and select Edit invoice or select Create invoice to create a new invoice.
In the Invoice no. field, enter the custom number or letter sequence you want to use for your forms. The sequence you set here applies to all sales forms.
Select Save.
Once you create a new invoice, it'll follow the number sequence you've set up.