Does a foreign company need a NEQ to do business in Quebec?

Yes, a company incorporated outside Quebec that carries on activities there must register with the Registraire des entreprises within 60 days of starting those activities, and it then receives a NEQ. Registration requires an address in Quebec where mail and official documents can be received, which is exactly what an Ancre address provides. A single occasional sale to a Quebec customer usually does not trigger the obligation, but an establishment, an employee, or regular activity does. Ancre supplies the address and the proof; filing the registration application remains up to you or your advisor.