I have just started using QB and need to change the starting sequence of my invoices to tally with my existing accounts, can anybody help?

use the gear menu, and select custom forms styles ( or what ever is close) in the content section>header enable custom transaction numbers.  After that you can enter an invoice number and after you save it, QB will increment from there, or enter a new custom number as you wish

Thanks for coming to the Community for help, @jrhughes100.

Rustler is right. You can use the Custom Transaction Numbers feature to change the invoice starting number.

Here’s a detailed instruction on how to turn it on in QuickBooks Online:

1. Go to the Gear icon and select Account and Settings.
2. Pick the Sales tab from the left menu.
3. Click the pencil icon on the Sales form content section.
4. Mark the Custom transaction numbers box.
5. Hit Save, then Done.

For more information, take a look at this article: Change the number on invoices or other transactions. Check out this link for additional reference: Change an invoice number. It contains a short video tutorial on how to perform the steps.

Let me know in the comment section below if you ever need anything else. Wishing you the best!