cinvio vouchers MUST NOT be included in the VAT return as they are defined as multi-purpose vouchers, which means that you can use them for different service providers in each EU Member State to pay for different services. What you MUST include in the VAT return are the monthly invoices you receive from cinvio service providers. 

More information can be found in circular 2018 / C / 127 regarding the VAT treatment of vouchers.