Internet invoice without Peppol

Hello. I would like to enter internet as an expense, but my vAT number is not on the invoice. Is it correct that I can then enter x% of the cost including vAT? For example: the invoice states €100 excluding vAT, so the price is €121 including vAT. Do I then enter an expense of 70% of €120 and tick ‘vAT declaration’? Thanks!