The CSAT is on November 19, a little over five weeks away. At this point, how you fill in the answer sheet matters more than mock-exam scores for some students. It is genuinely possible to solve a question correctly and still get zero because of how it was marked, or to get another subject's score by writing the elective order the wrong way round. This article is based on the answer-sheet instructions in the "2027 College Scholastic Ability Test Implementation Guidelines," published by the Korea Institute for Curriculum and Evaluation in August 2026, and lists what to get used to before test day. Details of operation follow the instructions of the test site and proctors, so confirm the final points with your admission ticket and the notices at your test site.

Use only a black computer marker on the answer sheet

The guidelines say to complete the answer sheet using only a black computer marker pen. Using any other pen can put the test taker at a disadvantage, and because answer sheets are scored by an image scanner, the guidelines state that pencils and mechanical pencils must never be used. You may use a black pencil or mechanical pencil for working in the question booklet, but when you transfer your answers you have to switch to the marker. You may bring your own marker, and test rooms also hand them out. The conditions for a personal marker that complies with the rules are covered in detail in our article on the self-scoring sheet and personal markers.

Marking two answers on one question scores that question zero

The scoring rule is simple. Regardless of the writing tool, a question where you mark two or more answers, or mark incompletely so that the machine reads it as an error, is scored zero. Short-answer questions in mathematics are the exception. The guidelines' examples of incomplete marking are filling only around the circle, filling only the middle, scratching with a knife, and leaving traces of an erasure. Incomplete marking is the most common mistake when you are pressed for time, so you need to practice filling the bubble completely in one go.

Preliminary marking is read as duplicate answers

The guidelines state that, regardless of the type of pen, preliminary marking may be scored as duplicate answers and put you at a disadvantage. If you have a habit of marking an undecided question first and changing it later, you should change that now. It is safer to note it in the question booklet and transfer only your final answers to the answer sheet. You must not make any other kind of mark on the answer sheet, and you must not crumple it or soil it with foreign substances such as gum or candy. The guidelines also say that any disadvantage arising from such problems is for the test taker to bear.

Correct mistakes only with white correction tape

To change an answer you have already marked, erase it completely with white correction tape and then mark again. Using correction fluid or correction stickers can put you at a disadvantage. You may bring your own tape, and proctors also lend it to test takers who want it. However, responsibility for incomplete corrections, such as tape that peels off, lies with the test taker. The guidelines also say that you can ask to replace your answer sheet if you find correcting difficult. It is better to request a replacement before the sheet gets messy.

Start with your examinee number, test-type and handwriting-check boxes

Write your name in neat Hangul block letters, and write your examinee number in Arabic numerals first, then mark the matching digit boxes. You must also write the handwriting-check phrase printed on the cover of each period's question booklet in neat letters with the black computer marker, and the proctor uses it to confirm your identity. For periods 1, 2 and 3 and the Korean History section of period 4, an examinee number ending in an odd digit receives the odd-type booklet and an even digit the even-type. You must check the type of the booklet you were given and mark it in the test-type box on the answer sheet. Leaving out or getting the test type wrong is also the test taker's own responsibility.

Mark short-answer math answers by place value

Short-answer responses in period 2 mathematics are written in decimal numbers and must be marked to match the hundreds, tens and ones places. When the answer is a single digit, it is accepted whether or not you mark 0 in the tens place. For example, if the answer is 8, marking either 08 or 8 is scored as correct. Conversely, marking the digits out of place makes the answer wrong. The moment of transferring answers after finishing a solution is when it is easiest to rush, so leave time to check the short-answer questions on their own.

For the inquiry section, follow the selection order on the admission ticket sticker

In the period 4 inquiry section, the first-choice and second-choice order written on the admission ticket sticker must match the order of elective subjects on the answer sheet. For example, if the sticker lists Korean Geography as the first choice and World Geography as the second choice, mark the Korean Geography answers in the first-choice box and the World Geography answers in the second-choice box. Scoring also follows the order on the sticker, so do not write them in the order you took them or whichever order is easier to read. If you chose only one social studies subject, you wait during the first 30 minutes and take it in the second period, and mark the answers on the first-choice answer sheet. The order of period 4 is explained in our article on period 4 Korean History and inquiry.

After the end bell, do not change a single box

Alongside the marking rules, time is something you must respect. Writing answers after the end bell of each period, including filling in the self-scoring sheet, is treated as cheating. The test room has no separate clock and runs on bell chimes and announcements, so you need to bring your own analog watch with hour and minute hands. These standards are set out in our article on CSAT watches and prohibited items, and how each type of cheating is handled is covered in our article on CSAT cheating penalties. What to do from today is simple: fill in your remaining mock-exam answer sheets exactly as you will on test day. Get used to filling the bubble in one go with the marker, correcting with correction tape when needed, and checking the order of electives. This article is general information, and if the test-site instructions and a proctor's instructions differ, follow the proctor.