Pet-related fees across Spanish accommodation generally fall into the same categories found elsewhere in Europe: a one-time cleaning fee, a per-night or per-stay charge, or occasionally a refundable deposit. Which one you'll meet depends heavily on the property type — casas rurales and self-catering rentals lean toward a flat one-off fee, while hotels more often add a per-night charge instead.
Since Ley 7/2023 requires any establishment admitting pets to specify fees in writing as part of its pet policy, this is one area where the law has made the figure easier to pin down than it might be in a country without that requirement — though in practice, the written policy isn't always posted prominently online, so a direct message or call is still the reliable way to confirm it.
Refundable deposits specifically for pets are relatively uncommon in mainstream Spanish accommodation, appearing more often at higher-end properties. Always get the figure confirmed in euros and in writing before arrival — a fee mentioned informally over the phone, especially at a smaller family-run property, can sometimes differ from what actually appears on the final bill if it wasn't pinned down clearly in advance.