Credit Score Guidelines for Debit and Credit Card Use

To manage your credit score, use your cards regularly within an amount you can repay. Debit card usage is also reflected in credit assessments. Credit cards can help you build a repayment history without late payments. Using both cards does not, by itself, raise your score.

The bonus-point figures are based on past guidance from the Financial Supervisory Service. Check KCB and NICE disclosures for current conditions. (Verified information from past Financial Supervisory Service guidance: using a debit card without late payments for at least 300,000 won a month for 6 months, or using it consistently for 6~12 months, could earn 4~40 bonus points · source: citigold.co.kr · checked 2026-10-13)

Comparing Debit Cards and Credit Cards

Both cards are used in credit assessments, but they differ in how payments are made. Debit card payments generally come from the balance in a linked account. With a credit card, you spend within the limit set by the card issuer and repay the amount later. Choose based on how much money you can have available by the payment due date.

NICE explains that debit card usage is also reflected in credit assessments. Responsible credit card use can also be assessed positively. See NICE's key assessment factors for details.

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Use a credit card for amounts you can repay and pay the bill on its due date.

How Much Will My Score Rise If I Spend 300,000 Won a Month on a Debit Card?

Spending 300,000 won a month alone is not enough to calculate how much your current credit score will rise. The often-cited 4~40 points comes from past bonus-point guidance issued by the Financial Supervisory Service. That guidance also lists conditions that could make someone ineligible for bonus points.

The Financial Supervisory Service's “Tips for Improving My Credit Rating (3): How to Earn Bonus Points in Personal Credit Assessments” states:

You do not need to submit your usage history separately.

This refers to debit card usage information received from financial institutions. Check with the credit bureau you use for its current, detailed conditions. The past document is available in the Financial Supervisory Service guidance posted by Citibank Korea.

Spending more on a debit card does not raise your score by a corresponding amount. KCB identifies consistent debit card use as a positive assessment factor. Your final score also reflects other information, including outstanding loans and late payments.

Should I Use 30~50% of My Credit Card Limit?

The disclosures reviewed do not present 30~50% of the limit as a common bonus-point criterion. Credit limit utilization means how much you have spent relative to your limit. KCB identifies an increase in the amount used relative to the limit as a negative factor. That does not mean keeping utilization below a particular percentage guarantees a higher score.

The formula for understanding credit limit utilization is:

한도 사용률(%) = 이용금액 ÷ 이용한도 × 100

This formula cannot calculate how much your credit score will change. Check how each service calculates the amount it displays as used. See the KCB guide to credit card limit use for more information.

• Lowering your limit does not reduce the amount you have already spent.
• If the amount spent stays the same, a lower limit means higher utilization.
• Raising your limit does not increase the amount you can actually repay.
• Do not increase unnecessary spending to meet a target percentage.

If you want a higher limit, check the card issuer's app to see whether you can request a review. Ask the card issuer what documents you need, such as proof of income. You do not need to raise your limit to the maximum just to manage your score.

How to Choose a Card for Your Situation

Which card to choose depends on whether you can have the money available by the payment due date. The table below gives guidelines based on how each card is paid. It does not predict the effect of any particular combination on your score.

Using both cards is one way to manage your spending. KCB's recommended card usage ratio may also differ from actual changes in your score. This limitation is stated in KCB's credit improvement guidance.

Common Mistakes When Closing an Old Card

Closing an old card does not immediately erase all its transaction history. KCB explains that it continues to use the information for a period after closure. You therefore do not need to keep every card just because it is old.

A long history of transactions in good standing is a positive assessment factor. However, the effect of closing an individual card cannot be calculated in the same way for everyone. See the KCB Q&A on holding and closing cards for more information.

How Are Installments, Cash Advances, and Card Loans Different?

Card purchases and card loans are not the same type of transaction. NICE explains that habitually making excessive installment purchases may be assessed negatively. It also identifies frequent cash advances as a negative factor.

With revolving payments, the amount you do not repay carries over to the next month. Fees under the agreement apply to the carried-over amount. See the KB Kookmin Card disclosure guide for the terms and payment structure.

Debit Card Small-Credit Payments Are Handled Differently for Billing and Deductions

If a debit card transaction is approved through a small-credit feature, you must repay it later. Treating it like a regular debit card payment could cause you to miss a bill. Check the separate withdrawal date for postpaid transit charges, too.

KB Kookmin Card's guidance states that amounts approved through the small-credit feature are billed separately. If payment is late, the same late-payment interest rate as for a credit card applies. Amounts approved on credit through this service are also treated as credit card spending for income tax deduction purposes.

Do not judge every transaction by the debit card label on the card. It is more accurate to check how the transaction was approved in your payment history. The source for this example is the KB Kookmin Card small-credit payment service guide.

Income Tax Deductions and Credit Scores Follow Separate Rules

A higher income tax deduction rate for debit cards does not mean they are better for your credit score. The National Tax Service identifies spending more than 25% of gross salary as a basic requirement for the deduction. Whether an expense qualifies for the deduction is determined separately.

These percentages are not refund rates that return the stated share of your spending. An income tax deduction reduces the income used to calculate tax. Separate deduction rates may apply to traditional markets and other spending. Check the conditions for each tax year in the National Tax Service Q&A on credit card and other spending.

If Your Score Stays the Same Despite Regular Card Use

Before increasing your card spending, check what information has been reflected in changes to your score. KCB and NICE each calculate scores using their own assessment systems. Their scores may move differently over the same period.

1. Check the credit bureau's name and the information's as-of date on the score screen.
2. Check whether your card usage or outstanding loan balance has changed.
3. Check whether late payments or transactions that are not yours have been recorded.
4. If you suspect an error, ask the relevant financial institution and credit bureau about correcting it.

The fact that you checked your credit score is not itself used in the assessment. KCB says it also uses nonfinancial payment information as a bonus-point factor. Check the credit bureau's service to see what information you can register. See KCB's key assessment areas for personal credit scores.