Amend Invoice to Tax Invoice

Hello,
i would like to know how do i amend invoice to tax invoice as i cant find the html code.

If you select a tax code that is known to require this change, it happens automatically. See this Guide: https://www.manager.io/guides/10388. Otherwise, see this Guide: https://www.manager.io/guides/7877.

looks for shaking head emojiā€¦ and then goes back to his own cave

if your using the latest version of Manager, then the Indian tax codes are in-built.
you will have to set your tax codes under settings.
then if you select one of these tax codes while making a sales invoice, the title will automatically change to Tax Invoice.