When you take the official TOEIC test, you will get a copy of your score. The scores come from ETS (based in New Jersey, USA), but you might receive it through your employer or school. The time it takes to get a score for the standard test (Listening and Reading) varies as it is a paper based test. If you do the optional Speaking and Writing test, you'll get your score in 3-4 weeks. Being done on the computer allows it to be graded faster.
You score for either test is valid for 2 years at most. It's not valid longer than that as your skills may improve or possibly decline. There's no time limit on how soon you can take the test again if your score isn't as high as you were hoping for the first time. There's also no limit to how many times you can take the TOEIC test.
So how is the TOEIC test scored? The Listening and Reading sections are scored separately. All questions are worth one point. There are 100 questions in each of the Reading and Listening sections, yet the maximum score for each is 495. If you got 0 out of 100, you get a 5 when it's scaled. How can that be? ETS uses some "magic" (how it's done is kept secret) to create it's scaled score. Your total score is the sum of your Listening and Reading scaled scores. The range is 10-990.
When you receive your score report, you also receive a certificate which can be one of 5 possible colours, depending on what your combined scale score for Listening and Reading is. The colour and corresponding scores are orange (10-215), brown (220-465), green (470-725), blue (730-855), or gold (860-990). Generally, a score range of 800 or more is considered advanced proficiency, 600-700 is high intermediate, 400-600 is intermediate, and less than 400 means the proficiency of a beginner.
The score report contains other details as well. The most valuable of these is the score descriptor section. It provides detailed information of your strengths and weaknesses based on your score. You can read the details here. There is also a percentile rank given. The percentile rank value indicates the percentage of TOEIC test takers, from a period of the 3 previous years, that scored below you. The last section is the abilities measured section. There are 4 categories for Listening and 5 categories for Reading. This data shows you the percentage of questions answered correctly for each of these categories. If you took the test at a company, the company gets all the score information from ETS. The score report you get from the company may not include all these details, it depends on the company's policy.
With the updates to the TOEIC test implemented worldwide in spring 2018, there is an additional ability reported for Listening. Thus there are now 5, not 4, categories in the abilities measured section for Listening. The new one is "Able to understand a speaker's purpose or implied meaning in a phrase or sentence".
The optional Speaking and Writing test is scored differently. Each section has a scaled score of 0-200 which is a conversion of the sum of the values you get for each question. The value of the questions varies in both Speaking and Writing. In Speaking, questions 1-9 have a maximum value of 3 while questions 10-11 have a maximum value of 5. In Writing, questions 1-5 have a maximum value of 3, for questions 6-7 it's 4 and for question 8 it's 5. You can't score less than 0 on any question.
In addition to a score, you are also given a proficiency level. Speaking has 8 levels and writing as 9. This is like the score descriptor section in the standard TOEIC test. You can read the strengths and weaknesses assigned to each proficiency level here.
Thousands of companies and institutions use the TOEIC test to measure the English skills of their employees because the scores can be trusted. The tests are marked by rigorously trained ETS graders following strict rules to guarantee consistency. This ensures scores that are fair, reliable and consistent year after year. That's why the TOEIC test is relied on throughout the world for over 35 years now.
What score should you be aiming for? As high as you can of course. The company or institution you are applying to should be able to tell you what their minimum is. A score of 600 at least is usually needed if you're going to work overseas where English is the primary language.