Spain introduced the new energy certificate rules in June.
Under the regime, people selling or renting out properties in Spain need to have their property's energy efficiency measured by a registered assessor.
Owners of homes built before 2007 must obtain an energy rating while homes built after this date should — in theory — already have one.
But the UK's Telegraph newspaper warns against scams involving the new certificates.
A sample energy certificate
One form of these illegal operations involves unqualified assessors selling certificates cheaply.
Another sees assessors guaranteeing owners an 'A-rating', a practice which is illegal.
Some assessors are even failing to attend the premises.
"This is not acceptable in any way. The Royal Decree requires a skilled and authorized professional to survey the property,” Jose Antonio Galdón, president of the General Council of Industrial Engineering of Spain said.
The UK newspaper said the situation had been made more difficult by the fact that many people weren't sure if they needed a certificate.
Although homes built after 2007 should have a certificate, this is not always the case.
The key factors to keep in mind are that the certificate must be granted by an architect, engineer or qualified technician, and that these people need to have the official go-ahead to carry out building projects and thermal installations for buildings.
The Telegraph also warns that not all architects and engineers are authorized.
These professionals also need to be members of an official provincial association with a membership number.
In terms of prices for energy efficiency certificates, this should be about €200 and €300 per home (£170 and £260, $265 and $400), according to Galdón of the General Council of Industrial Engineering of Spain.
Once obtained, the certificate must be registered with local Spanish authorities — a procedure which differs around the country, with some regions demanding a fee of around €30.
After this registration, authorities issue and energy label which can then be used in dealing with real estate agents, buyers and tenants.
Fines for failure to comply with the news guidelines can mean fines of up to €6,000, The Telegraph said.