I am writing to alert those who want to go to Brazil: please insist on having your passport stamped before you enter the country, no matter which checkpoints you pass.
If the immigration officials forget to put a stamp on your passport, beg for one.
I have been travelling in Latin America for some time. Recently, I took a bus from Buenos Aires in Argentina to Puerto Iguazu which is situated on the Argentina-Brazil frontier, where I enjoyed the famous and spectacular view of the Iguazu Falls.
Then, as most travellers do, I changed to a bus which crosses the border to Brazil, to see the whole panoramic view of the falls. It took only 15 minutes to cross the border and arrive at the checkpoint. A Brazilian immigration officer came on to the bus to check the passports of the passengers.
I was checked too, of course. Nothing happened. All of us were let through without anyone having their passports stamped.
I took a flight back to Buenos Aires three days later and, at the airport of Sao Paulo, I was stunned to learn that I was to be fined US$130 (about HK$1,000) by the police (immigration).