The UK Government has added more countries to its travel red list and taken Portugal off its green list.
With Covid still widespread in many countries, tourists will have to think carefully about their spending on holidays.
Where will I be able to go on holiday?
England has a limited number of green list destinations, where people can travel without having to quarantine on their return (although they will still have to take a Covid test before and after the trip).
All other countries are rated amber or red, and travellers must quarantine after visiting them.
Portugal has now moved to the amber list, and seven other countries - including Sri Lanka and Egypt - have been added to the red list.
Can I cancel my holiday if it turns out I have to self-isolate on my return?
There is always a risk that a green-list country may move to the amber or red list.
If this happens you will need to quarantine after your holiday - something that could be difficult for many people.
Operators do not have to refund you if you are unexpectedly forced to self-isolate on your return.
It is best to study their policies before booking, or see whether they can offer some support if you have already booked and want to cancel.
Transport Secretary Grant Shapps has said that government advice is not to book any holiday which does not include a refund, in the event that the Covid-related situation changes.
Will I be refunded if my holiday is cancelled?
If the government announces that travel to a particular country is not advised, then airlines and travel companies are likely to cancel any pre-booked flights or holidays there.
If this happens, you are entitled to a full refund, and you can choose to receive that refund in cash.
An airline should refund the money within seven days, although some people have had to wait longer.
A package holiday should be refunded, in full, within 14 days.
What if I make a decision that it's too risky to travel?
This is far less clear-cut. If you cancel, rather than the travel provider doing so, then you have no automatic right to a refund.
In this situation, it is worth contacting the airline or holiday provider to see what options you have.
Some may allow you to transfer to another date or destination, they may give you a voucher, or they may allow you to cancel and get a refund.
Will travel insurance cover me if I get Covid?
Travel insurers are offering different levels of cover. In part, this depends on how much you pay for a policy.
The majority - but not all - will pay out if you test positive for Covid and have to cancel before you travel.
In most other Covid-related scenarios, only a minority of policies will give you financial cover, according to analysis by data specialists Defaqto.
For example, if a positive or missed Covid test stops you from boarding a flight back to the UK, only about one in 10 policies will cover you for any costs you incur as a result.
If the Foreign Office advises against travel to a country, then all but a handful of travel insurance policies would be invalid.
Does my insurance cover me in an amber-list country?
Anyone planning to travel to an amber-list country should look up their proposed destination on the Foreign Office (FCO)'s country-by-country list.
If the FCO advises against travel to a certain country, then travel insurance would almost always be invalid.
If not, then the cost of medical treatment abroad would be covered. In most cases that would include treatment if you contracted Covid.
However, although travel to amber-list destinations is allowed, the Department of Health still advises holidaymakers against it.
It is always worthwhile to have an EHIC (or its replacement, the GHIC) to cover healthcare in EU countries.
Why is this so complicated?
Rules are inevitably going to be complex, given that the risk of Covid varies so much between countries.
The government has published a charter that "clearly sets out consumer rights and responsibilities when booking travel while Covid-19 measures remain in place".
It says it expects travel operators to be "flexible" with customers, given the circumstances, and the Competition and Markets Authority (CMA) has warned package holiday firms that they must adhere to refund rules.