I am having a real headache managing invoice numbers. Multiple apps create their own invoice ID's which then screws up my next invoice number in QBO...

Hi there, dale.

I can see how you would want to get this resolved and understand your frustration. No worries I'm here to share some information regarding invoice numbers in QuickBooks Online (QBO).

QBO is dependent upon what the app shares with us. Thus, adopting the same invoice number from the application. 

As a workaround, we can manually change the invoice. When doing this, we'll have to turn on Custom transaction numbers first.

Here's how:

1. Go to the Gear icon in the top right of the page.
2. Select Account and Settings and click on Sales.
3. Tick the Custom transaction numbers box.
4. Hit Save and Done to close the page.

When done, we're now ready manually change the invoice numbers:

1. Go to Sales then select Invoices.
2. Locate the invoice you want to modify and click on the Pencil icon to edit.
3. Go to the Invoice no. field and change the invoice number.
4. Click on Save.

Additionally, here's an article that'll help you upload, edit, or delete logos from your invoices, estimates, or sales receipts: Add, customise, or remove logos on sales forms in QuickBooks Online.

Keep your post coming if you've got additional questions about invoices in QuickBooks Online. I'll be right here to assist you further. Take care.