Care homes for the elderly are being investigated by the competition watchdog following concerns over people potentially being faced with shock bills and "hidden" charges.
The Competition and Markets Authority (CMA) has launched a market study into the sector.
This will look at how people find the experience of choosing a care home, explore whether the current regulation and complaints system gives residents enough protection, and examine how well care homes are complying with their obligations under consumer law.
The CMA said it particularly wants to hear from care home residents and their relatives who have encountered issues such as unexplained or "hidden" charges, unexpected fee increases, confusing requests for "top-up" payments, or occasions when they feel that complaints have not been handled fairly.
Andrea Coscelli, CMA acting chief executive, said: "Choosing a care home can be emotional and costly.
"It's therefore essential that elderly people and their families have all the information they need to make the best possible choice, and then feel secure in the knowledge they will be fairly treated throughout their time there.
"We are undertaking a thorough review of the sector to make sure it works in the best interests of those who rely on it.
"We want to hear from care home providers about the services they offer and any challenges they face, as well as residents, families and charities who have experienced what it's like to choose and live in a care home.
"Given the concerns we have heard about possible breaches of consumer law, we particularly want to hear from people who think they might have encountered unfair terms or practices."
Around 430,000 older people are in care and nursing homes in the UK. The CMA wants to hear people's views by January 16 2017.
The market study will evaluate the effectiveness of competition between care homes in driving quality and value for money for residents and taxpayers.
"It will also consider how local authorities and other public bodies purchase and assign care home places, and how they encourage and shape local supply.
Market studies launched by the CMA can have a wide range of outcomes, including markets being given a clean bill of health, action being taken to improve levels of information given to consumers, law enforcement action, making recommendations to change regulations or encouraging businesses to self-regulate.
Citizens Advice has previously called for the CMA to investigate the care home market after its research found people were getting shock bills, having as little as a week's notice about fees going up, and paying deposits for which they were offered no protection.
Previous research by Citizens Advice found one in five people with family in a care home have been hit by a shock bill.
Gillian Guy, chief executive of Citizens Advice, said: "Our research finds people are experiencing a number of problems with the care market including short notice of cost increases and hidden charges, for things like management fees, which can run into thousands of pounds.
"People often have little choice but to pay these costs because moving the resident to another care home is simply too disruptive or distressing.
"In some instances relatives don't make a complaint to the company because they worry that the resident could be treated badly."
Vickie Sheriff, director of campaigns and communications at consumer group Which?, said: "We welcome the decision from the CMA to investigate this market and ensure that all providers are aware of their obligations under consumer law.
"This should help give consumers confidence they are being treated fairly."
People can email the CMA with their experiences at firstname.lastname@example.org.