Foreign tourists must now pay a 150,000 rupiah (£7.60; $9.60) levy to enter Bali, one of the world's most popular tourist destinations.
Indonesian authorities say this is aimed at protecting the island's environment and culture.
Bali is known for its pristine beaches and surfing waves, as well its beautiful landscapes.
Official data shows that almost 4.8 million tourists visited Bali between January and November last year.
The tourist tax, which was first announced last year, came into effect from Wednesday - Valentine's Day.
It applies to foreign tourists entering the province from abroad or other parts of the country, with domestic Indonesian tourists exempt. Travellers are urged to pay up before arrival, through the Love Bali website.
Tourism contributed some 60% to Bali's annual GDP before the pandemic.
According to the province's statistics bureau, Australia was the largest contributor of foreign tourists to Bali in November 2023 with more than 100,000 arrivals. This was followed by tourists from India, China and Singapore.
But misbehaving tourists in Bali have riled locals in recent years.
Last March, a Russian man was deported from Bali after stripping off on Mount Agung, believed by Hindus to be the home of the gods.
In the same month, authorities said they planned to ban foreign tourists from using motorbikes, after a spate of cases involving people breaking traffic laws.
In 2021, uproar also resulted when a three-minute video circulated of a Russian couple having sex on Mount Batur, another holy site.
The announcement came on the same day that millions of Indonesians headed to the polls to select a new president and legislature. More than 200 million people over Indonesia's 17,000 islands and across three time zones are eligible to vote.
