We lump them together as "the civil service exam", but national and local posts differ from eligibility through to the shape of the work. Because the subjects are similar, though, candidates start preparing without checking the differences and then hit a wall at the registration stage.

The first gate — residence requirements

The Grade 9 national open competition has no residence requirement. You can sit it wherever you live.

Local exams are different. Most local authorities outside Seoul require one of the following.

• Continuous resident registration in the area from 1 January of the exam year until the final exam date
• Or a record of at least three years' cumulative past residence in the area

This has to be checked when you start preparing. "I will move once I pass" does not work, because once the 1 January reference date has gone by, you cannot sit that year's exam at all.

Local means one place only — because the date is shared

The most frequently missed point. Local open competition written exams are held on the same day across the country. So a strategy of applying to several authorities at once does not exist. You can register with one local authority only.

Offices of education (for education administration posts) take registrations separately from local authorities, but the exam date is the same. In practice you sit only one. In other words, applying for a local post is a decision to choose one region, once a year.

The national and local exams, by contrast, are held at different times, so you can sit both in the same year. That is why many candidates sit the national exam first and prepare for the local one in light of the result.

The work and the workplace are different

Life after passing diverges too.

National posts are based in central government ministries and their affiliated bodies. You can be posted anywhere in the country — government complexes, agencies under a ministry, airports — and rotation every two or three years is usual. A relatively larger share of the work is planning and supporting policy.

Local posts are based in provincial, city, district and county offices and community service centres. The workplace tends to stay within one area of daily life, and a large share of the work involves dealing directly with residents.

This difference is not a matter of taste but a question of how you design your life. If family, housing and commuting have to stay fixed, a local post may fit; if you can accept relocation and want policy work, a national post may.

Where are the ratios lower?

People often say local exams are easier, but that is not accurate. The papers come from the same body, so the difficulty is similar. What differs is that the national exam draws applicants from the whole country and so concentrates competition, while local exams vary widely by area. Populous areas are no easier than the national exam; some areas are.

Choosing an area on the ratio alone is therefore risky. Residence requirements narrow the options from the outset, and you will be working there for years after passing. How the exam subjects changed is set out in the other articles in Civil Service Exams.

In summary

Three things to settle before you start preparing: (1) whether you meet the residence requirement for local posts (the reference date is 1 January), (2) that you can choose only one place for a local exam, and (3) that national and local exams can both be sat. Settle those three and the shape of a study plan follows.