Premium-rate telephone numbers are telephone numbers for telephone calls during which certain services are provided, and for which prices higher than normal are charged. Unlike a normal call, part of the call charge is paid to the service provider, thus enabling businesses to be funded via the calls. While the billing is different, calls are usually routed the same way they are for a toll-free telephone number, being anywhere despite the area code used. These telephone numbers are usually allocated from a national telephone numbering plan in such a way that they are easily distinguished from other numbers. Telephone companies typically offer blocking services to allow telephone customers to prevent access to these number ranges from their telephones. In some states, telephone companies are required by state law to offer such blocking.
In the United Kingdom, these numbers are issued to service providers through the regulatory body PhonepayPlus (originally known as ICSTIS, the Independent Committee for the Supervision of Standards of Telephone Information Services) to ensure certain community standards are adhered to both in terms of content and price. Charges are presented as part of the normal telephone bill.
Other UK numbers -- notably 0870 and 0871 -- are also charged at higher than standard rates. These have not technically been classed as premium rate numbers, but due to public disquiet over the charges, particularly for 0870, the regulations and prices for these numbers are being changed: 0871 is to be reclassified as premium rate, with all the regulations this status entails, while 0870 is still under review, though price and regulatory changes have both been suggested.
Adult chat lines (phone sex) and tech support are a very common use of premium-rate numbers. Other services include directory enquiries, weather forecasts, competitions and voting (especially relating to television shows). Diplomatic services, such as the US embassy in London or the UK Embassy in Washington, have also charged premium rates for calls from the general public.
Computer criminals have used premium-rate numbers to defraud unsuspecting Internet users. One scheme involved inducing users to download a program known as a dialer that surreptitiously dialed a premium-rate number, accumulating charges on the user's phone bill without their knowledge. Another now-uncommon premium-rate scam involves television programming that induces young children to dial the number, banking on the notion that they will be unaware of the charges that will be incurred. One variant, targeted at children too young to dial a number, enticed children to hold the phone up to the television set while the DTMF tones of the number were played. This type of scam was especially popular in the late '80s to early '90s in the United States before tougher regulations on the 900 number business forced many of these businesses to close.
Earlier, 976 numbers used 976 as a local prefix, though it was not assigned to a specific telephone exchange like other prefixes. These numbers were dialed as any other local number, such as 976-1234.
A call to either one of these numbers can result in a high per-minute or per-call charge. For example, a "psychic hotline" type of 1-900 number may charge $2.99 for the first minute and 99 cents for each additional minute.
Initially, consumers had no choice regarding the accessibility to 900/976 numbers on their phones. However, in 1987, after a child had accumulated a bill of $17,000, the California Public Utilities Commission subsequently required phone companies to give customers an option to prevent the dialing of 900/976 numbers.
In the early 1980s through the early 1990s, it was common to see commercials promoting 1-900 numbers to children featuring such things as characters famous from Saturday morning cartoons to Santa Claus. Due to complaints from parent groups about kids not knowing the dangers of such calls, such commercials ceased to air on television during the mid-1990s
900 numbers used for adult entertainment lines was a prevalent practice in the early years of the industry. This practice continues, along with the use of these numbers for things such as software technical support, banking access, and stock tips. Adult entertainment 900 numbers have been largely absent from AT&T and MCI since 1991 (except for a short time in 2000 when AT&T "looked the other way" in regards to adult services); the industry still suffers from the stigma attached to the early days of the industry when television had an onslaught of late-night television commercials with girls in hot tubs. In most cases, however, the caller got much less than he thought he was bargaining for.
Some uses of 1-900 numbers:
AT&T has confirmed that the Hulk Hogan Hotline was the most lucrative 900 line in the United States from 1991 through 1993. Other early leaders in amassing huge volumes of revenue were the New Kids on the Block and Dionne Warwick's "Psychic Friends Network".
Sometimes, these have 800 number standards, but charge a toll.
Consumers in the US have specific rights regarding 900 number calls, as laid down by the Federal Trade Commission. 
Most media who sponsor 900 number programs do so by working through a 900 number service bureau. A 900 number service bureau works through the carriers to gain approval for the 900 number program, then operates the equipment that processes the consumer's 900 number calls. MCI is currently the only 900 number provider in the United States that provides both transport and billing for 900 numbers. In an effort to keep its overhead down, MCI maintains relationships with only four service bureaus in the country who have direct billing relationships -- MVA, ICN, Spark Network Services, and Advanced Telecom Services
Telephone numbers of the form 0600-xxx-xxxx and 0609-xxx-xxxx are premium rate numbers. The 0609 series is for entertainment (fixed rate), while 0600 is for services (the rate depends on the particular number).
In Brazil, there is only one premium prefix: 0500, and this number is only used by Brazilian Internal Revenue Service (Receita Federal) to file for the Annual Federal Income Tax exemption, charged at a premium rate per call (not per minute).
A long time ago, 0900 was available, but now is no longer allowed. As there are no longer premium numbers, TV shows now use mobile numbers to receive calls and generate revenue to their program.
However, the regulation is very strict. TDC is the only carrier offering these numbers, with kwak Telecom offering numbers internationally. The regulator can be found at http://www.itst.dk/, a shortened English regulation is available here: Short Denmark Regulation
The Finnish Consumers’ Association has repeatedly denounced the use of premium rate numbers.
There are also special 4 digits numbers in the form of 32xx, for which billing rules can be the ones from any 08xx number, to the provider's choice.
The split rule between different premium rate numbers is not clearly defined (premium rate information numbers and premium rate entertainment numbers).
The regulator (ARCEP, previously ART) has also issued new range for Telephony over xDSL in the 087x range which might confuse consumers, as calls to these numbers are billed as local calls nationwide. They will be superseded by the 09xx range in the future.
All 15x numbers have officially quoted rates, set by the prefix, although telecom providers can charge an additional fee for carrying the call. 151x numbers are charged on a per-call basis, all others on a per-minute basis. In general the prices increase as the prefix number increases, within the call type range.
Regtel is a body which monitors the premium rate services industry in Ireland. Although an independent body, it can impose sanctions, ban advertisements and ban services offered by providers. It is funded by a levy on providers.
Effective on December 1, 2008, 300 and 400 numbers are changed into 703 and 704 respectively, freeing up the whole 30x and 40x range for the future assignments (non-premium rate). This change will allow to accumulate all the premium rate services in the 700-709 range of numbers.
Prior to 2002, all numbers starting with 89 were premium rate numbers. Some of those number remain as local premium numbers, and the 02xx89xxxxx block remains reserved.
Also there are other range for information services (weather, white pages, etc...), there are all the numbers starting with 118, they can have 5 or 6 digits with a variable cost per number. 11823 is free from Telefónica's telephone cabins. Previously 11823 was 1003.
See also Bundesamt für Kommunikation
PhonepayPlus (originally called ICSTIS) is the governing body that regulates premium rate services in the UK. They are responsible for investigating complaints, and to ensure that information and service providers comply with a Code of Conduct. Although an independent body, PhonepayPlus can impose sanctions upon providers found to be in breach of the Code of Practice, including a levy and a ban on the service.
Information providers in the United States who advertise in magazines should consider easy expansion to the United Kingdom since many magazines are sold in both countries. This often entails simply adding an additional phone number to the existing advertisements.
Late night TV game shows in the UK such as the Mint, and also BBC's Blue Peter and Channel Four's Richard & Judy programme, were recently (early-to-mid 2007) investigated for phone call irregularities relating to premium rate dialled numbers.
Other numbers beginning with 19 are generally used for premium rate short message service (SMS) services on mobile phones. These were originally trialled using the 188 prefix.
Previously (before the introduction of eight digit numbering), the prefix 0055 was used for this purpose, and as a result 190x numbers are occasionally referred to colloquially as 0055 numbers (pronounced double-oh, double-five).

Since these kinds of numbers have confused international jurisdiction, they are also sometimes used for fraud.