The starting point is the EU product intervention regime from ESMA, which the CNMV applies in Spain. For retail contracts for difference, providers may not use bonuses or other incentives to attract or reward clients. Deposit matches, welcome credits and volume-based cash rewards on CFD or forex accounts are not permitted for Spanish retail traders.
The CNMV has layered extra restrictions on top. It limits aggressive marketing of CFDs, restricts sponsorship and brand advertising where the aim is to promote these products, and prohibits paying clients to bring in new clients. So even the marketing around CFDs is constrained in Spain, not just the bonuses themselves.
These rules target leveraged CFD products specifically. They do not reach every offer. A broker that gives you access to real shares may still run a free-share or commission-rebate promotion on a stock account, and crypto platforms operating under their own registration can still offer sign-up rewards. If an incentive is tied to CFDs or forex and aimed at Spanish residents, though, a compliant firm will not be paying it.