I contacted the Palacio on line and was advised that securing a pre-booking was not possible.My understanding is that the tickets are sold at the Palacio, with tours in different languages run on a schedule determined each day according to who is buying tickets. We went on a Sunday morning, bought tickets ( half price for seniors) about 10.30 for a tour at 12..00. We used the time well by a visit to San Francisco just around the corner but there is lots to do in the area as well. The tour is good.

Thanks all. This was the response directly from Palacio da Bolsa:

Even if you buy the tickets on line, you still must come to our ticket office to see what tours are available that moment, do the line and book your place in one of them (guided tours are mandatory)!

We hereby inform you that the reservations for visits are made directly in our ticket office, when you purchase the tickets.

Therefore, the email we send you is intended to explain how visits to our building work, and cannot be considered as a reservation.

In response to your email we hereby inform you that the first person who buys the tickets decides the language of the tour. Being so, I cannot tell you in advance which language will depart at what time. We do tours in Portuguese, English, French and Spanish and we have tours starting every 20/30 minutes. So we advise you to come to our ticket office as soon as you can so that you can choose the time you prefer.

I don't know for sure, but I suspect not. I couldn't find any online booking ability either. The building is still used for meetings of the Commercial Association and private functions and I would assume those take preference over visitor tours. So I doubt they would accept visitor tours too far in advance anyway.

We went to the building and bought tickets for an English language tour a couple of hours later. So we had virtually no line ups and we thoroughly enjoyed the short tour of the impressive building.

Sorry I’m not sure we just bought our tickets once there, which a lot of people seem to do

Sorry. We bought them there no idea of on line