Stage 1 of the buying process

Stage 1: Preliminary "promissory buying and selling" contract

Once a price has been agreed with the vendor both parties will sign a preliminary "promissory buying and selling" contract, called a Contrato de Promessa de Compra e Venda and the buyer will make a deposit of 10%-30% of the purchase price (except in the case of new constructions where this deposit will be considerably less). The deposit can vary depending on the price, location and the real estate agency you work with. Many purchasers also hire a lawyer to help to negotiate a 10% percent deposit, opposed to paying a larger deposit. The "promissory" contract, similar to an exchange of contracts in the UK, legally secures the purchase, and is subject to satisfactory searches having been returned. The Portuguese law protects both parties involved. The deposit is forfeited if the purchaser does not proceed, and if the vendor withdraws double the deposit is paid to the purchaser by the vendor. This contract must be signed in the presence of the Notary.
Before signing the a preliminary "promissory buying and selling" contract, you or your legal representative will need to obtain the following legal documents:

Property Registration Certificate (Certidão de Teor)

At the local Land Registry (Conservatória do Registo Perdial) check if the seller has the ownership of the property and no one else has those rights and also if it is free of charges, mortgages and other debts. A Registration Certificate should be issued with a time limit. The Registration Certificate describes the property's legal history and proof of ownership. The Registration Certificate is required to perform the completion process at the Notary's office. In some cases it can take some time before debts are registered against a property and therefore it is advisable to instruct your Advogado to check with the Conservatória do Registo Predial on the day of completion to ensure the property is still free from debt.

Property Tax document (Caderneta Perdial)

At the local tax office obtain an official tax document. The official tax document certifies the inscription of the property for fiscal purposes, the current owner and their fiscal number, a description of the property, and the property's unique fiscal number. The official tax document mentions how much the owner will pay in local yearly taxes and should detail the property's size, location, boundaries and a brief description. In some cases there maybe a drawing outlining the plot size and buildings.
If the property is new then the official tax document will not exist in and a temporary certificate will be issued by the building developer.

License of Use (Licença de Utilização)

Obtain a copy of the usage license from the Local Town Hall. In this document you can check if the property is approved for the proposes of the original building permission. For residential property it is necessary to have a habitation license. Houses built or altered after 1 January 2003 in Portugal are required by law to have a Ficha Technica de Habitação. This document contains information about the property including builder details, materials used and so on.
For non residential it is necessary to have a commercial or industrial license. This usage license document needs to be presented at the stage of signing the "promissory buying and selling" contract..