How can i customise expense,journal etc voucher formats

The form styles in QuickBooks Online are for sales transactions, 

sudheendran-mg-h.

The option to modify a voucher isn't available. We can look for a third-party app that can edit the details of the Voucher.

 Though, we can edit the color, font, and positioning of your company logo. It modifies your Standard template. The design of this template will affect how your Voucher looks like.

These are the articles you can check for your guide:

• Add, customise, or remove logos on sales forms
• Customise Forms

Let me know if there's anything that I can help. Keep safe!