New rules forcing broadband firms to be clearer in adverts on the costs of their contracts have come into effect.
Broadband suppliers will now have to show upfront and monthly costs, without separating out line rental prices, according to the changes brought in by the Advertising Standards Authority.
The rules were originally due to be implemented in May, but firms asked for more time to comply with the changes.
The ASA said customers were now much less likely to be misled.
"The effect should be a real positive difference in how consumers understand and engage with ads for broadband services," said ASA chief executive Guy Parker.
The move comes after research by the ASA, conducted with regulator Ofcom last year, found that most users could not correctly calculate bills based on the information given in a selection of broadband ads.
People were "likely to be confused and misled" by price claims in the adverts, the ASA found.
Geoff Roberts, from Northampton, told the BBC that he found broadband adverts "completely misleading".
"What was advertised up front - when you really went into it - was nothing like what they were offering. The monthly amount was not clear."
He was paying nearly £45 for his phone and broadband, but reduced that amount to £26.50 when he switched to another provider.
To comply with the new rules, broadband providers will now have to:
- Show all-inclusive, upfront and monthly costs, with no separating out of line rental prices
- Give greater prominence to the contract length and any post-discount pricing
- Give greater prominence to upfront costs
Digital and Culture Minister Matt Hancock welcomed the ASA's move.
"Making broadband providers show all-inclusive, upfront prices in their advertisements means consumers will be much better placed to make an informed choice when deciding on a service," he added.
Technology expert Chris Green told BBC Radio 5 live: "It's going to level the playing field, and make pricing more transparent.
"But mostly it's about providing a lot more clarity to customers."
However, there will be no change to the rules on the way providers are allowed to advertise the broadband speeds on offer.
"If a broadband company advertises a particular speed, actually only up to 10% of people need to get that speed, which a lot of people would say is quite misleading," said Steve Nowottny from Moneysavingexpert.
One reason for that rule is that different customers will experience different speeds, according to how far they live from the telephone exchange.