How/where the Social Security number is used?

You use your social security number in contact with authorities and private companies because that number is your identity number in Sweden. The Swedish Tax Agency has instructions from the Government to provide up-to-date and correct information about those who live in Sweden so that other authorities have the basis for planning and making decisions. This is done by informing other authorities about your status by public register of information. They get the right information about you when there are changes in the population register, for example about your address when you report moving to a new address. Private companies can also get their customers' records updated via the National Personal Address Register (SPAR).

The structure of Swedish Personal Identification Number:

The person number indicates your birth date and time followed by one control digits (with a 123456-7890 format). The only information that one can read from a social security number is birth date and sex. The gender is shown in the second-last digit of the person number.

For Example, a person who is born on August 23^rd, 1964 gets a personal identification number starting with 640823. The birth number consists of three digits. The last number is odd if your legal gender is male and even if your legal gender is female. Between the birth time and the birth number, there is a hyphen (-), which is replaced by a plus sign (+) the year a person turns 100 years.

The digits of birth numbers is limited. Therefore, the some birth numbers may have been already taken for a certain day. Then you can get a social security number where the numbers for the birthday are a day that is close to your real birthday. 

The last digit in the personal number is a control digit. It is calculated mechanically based on the birth time and the birth number.

Coordination Number (Samordningsnummer):

Coordination number is an identification number for people who are not or have not been registered in Sweden. The purpose of the coordination number is that authorities and other social functions should be able to identify persons even if they are not registered in Sweden. Coordination numbers can be used in contact with various authorities, healthcare and banks. You can get a registration approval (registerutdrag) from the population register showing your coordination number. 

Who can get the coordination number?

You who do not have a personal identification number but have or need to contact with authorities in Sweden can get a coordination number. The Tax Agency will give you a coordination number if you have got work in Sweden and will pay tax or if you have your own company that will be registered with the Tax Agency.

It is the authority that you have contact with who orders a coordination number for you. All state authorities and certain private colleges have the right to request coordination numbers.

A coordination number which is issued for a person will be valid for lifetime and there can never be two identical coordination numbers for different individuals. If you who have received a coordination number are registered in the system later, your coordination number will be replaced by a social security number. 

The Tax Agency records an address for you who have a coordination number. If your identity is established, the Swedish Tax Agency will also update the address in the National Address Register (SPAR).

The structure of Swedish coordination number:

Coordination numbers as well as social security numbers consist of ten digits. The initial six digits are based on your birth time. Birth time is the year, month and day you were born. The number for your birthday is increased by the number 60 in coordination number. For example: 

Coordination number for a man who was born on October 3^rd, 1970 and has an individual number as 239 will be: 

70 10 03 + 60 = 701063-2391

(Extracted from skatteverket's websites. Last updated on 2019-03-08)