Can I use R-404A in new equipment?

Legally yes, until 31/12/2019. However, the customer would be getting a poor deal as servicing and maintenance with virgin product is banned from 01/01/2020.  At some stage before the end of its useful working life the equipment would need to be retrofitted to a lower GWP refrigerant, such as Opteon XP40 (R449A). It would be sensible to start using a Lower GWP refrigerant in new equipment now, rather than needing a conversion at a later date.  See other FAQs.