How to add line item property field to the checkout template?

Hi Shopify member,

I would like to have the function of adding a tickbox to the checkout template so I can get the information if my customer want an invoice send to their email or not. I know this can be simply adding a line-item property field to collect the data, but I couldn’t figure out how to get to the checkout template? or anywhere I can put this field in so that it showed up in the order at the admin page?

Tick this box to get a copy of invoice

Thanks for the help in advance.