Credit Score Guidelines for Debit and Credit Card Use

Regular debit card use and a sound credit card repayment history can help your credit assessment. When choosing a card, consider your ability to repay and your card use history rather than treating past bonus-point guidance as a guaranteed credit score increase today.

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.

Comparison Debit card Credit card
Typical payment method Payment amount is withdrawn from a linked account Amount spent is repaid on a set payment due date
Spending limit Account balance and card spending limit Credit limit set by the card issuer
Information used in credit assessments Consistent usage history Usage and repayment history, among other information
What to manage Whether postpaid transit or small-credit payments are enabled Upcoming payment amount and outstanding balance
How to choose Whether it is convenient to spend within your account balance Whether you can pay the billed amount on the 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.

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.

Item in past guidance Explanation at the time What to keep in mind now
Spending amount and duration At least 300,000 won a month for at least 6 months Cannot be assumed to be a current common requirement across all credit bureaus
Consistent use Consistent use for 6~12 months Does not mean your score will rise just because you meet the duration requirement
Bonus-point range 4~40 points Does not guarantee that an individual's final score will rise by that amount
People who may be subject to restrictions People with late payments or a history of late payments, multiple debts, or cash advance use, among others Bonus points may be unavailable or limited depending on individual circumstances

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.

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.

Current situation How to choose What else to check
You want to spend within your account balance Consider mainly using a debit card Whether you have signed up for postpaid payment features
You can reliably pay your credit card bill Use the card consistently for necessary spending Upcoming payment amount and balance in the account used for automatic payments
You spend close to your credit card limit Review total spending and unpaid amounts Changes in the amount used relative to your limit
You are short of money on each payment due date Prioritize reducing additional spending and making a repayment plan Whether you use card loans or revolving payments
You already use both cards Divide spending between them within your total budget Each card's billing date and overlapping expenses

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.

Common assumption What to check
Closing a card immediately deletes all past usage history Credit transaction information may still be used for a period after closure
Old cards must be kept Consider the annual fee and whether you actually need the card
Each additional card raises your credit score The number of cards you hold and your usage and repayment history are different pieces of information
Closing a card eliminates its remaining balance Unpaid bills and installment balances must still be repaid after closure

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.

Type Meaning What to manage
Single payment Pay the purchase amount on the set payment due date Check whether you can pay the billed amount
Installments Pay the purchase amount over several payments Check the remaining installment balance
Short-term card loan or cash advance A short-term loan within your card limit Review repeated use and the repayment burden
Long-term card loan A loan provided by the card issuer Check the interest rate, repayment period, and outstanding loan balance
Partial payment carryover agreement or revolving payment Carry part of a payment over to the next due date Check the carried-over balance and fees

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.

What to check Where to check
Whether the transaction was a regular debit payment or a small-credit approval Approval notification and transaction details
Whether there is an amount to pay later Card statement
The actual withdrawal date Card issuer's payment information
How the transaction was classified for income tax deductions Certificate of credit card and other spending

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.

Payment method for ordinary spending Income tax deduction rate
Credit card 15%
Debit card 30%

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.

FAQ

Can using only a debit card help your credit score?

Consistent debit card use is also reflected in credit assessments. You do not need to get a new credit card just for your credit score. Your actual score is also affected by other information, including loans and overdue payments.

Will spending 300,000 won a month on a debit card raise my score by 40 points?

You cannot assume this is a universal rule for score increases today. The figures of at least 300,000 won per month and up to 40 points come from past guidance on bonus points issued by the Financial Supervisory Service. Check the current criteria with the relevant credit bureau.

Do I need to use at least 30% of my credit card limit?

The disclosures reviewed do not state a common requirement to use at least 30% of your limit. You do not need to spend more just to reach a certain percentage. Spend only what you can pay on your payment date.

Will raising my credit card limit also raise my score?

A higher limit alone does not guarantee a higher score. If your spending stays the same, the percentage of your limit that you use goes down. Your ability to repay and other transaction information are also reflected in the assessment.

If I close an old credit card, does its transaction history disappear immediately?

KCB says it continues to use transaction information for a certain period after a card is closed. It would be inaccurate to assume that all its history is deleted immediately. When deciding whether to keep it, also consider the annual fee and whether you actually need it.

Can a debit card have overdue payments?

Using a postpaid transit or small credit feature means you will have an amount to pay later. In addition to regular debit card payments, check the billing date and the account the payment will be withdrawn from.

Does the debit card income deduction rate also apply to payments made using a debit card's small credit feature?

You cannot assume they are treated the same as regular debit card payments. KB국민카드 says payments approved under the small credit feature count as credit card spending for income deduction purposes. Check how they are classified on the certificate from your card issuer.

Does repaying a cash advance on time mean it will not affect my credit assessment?

Your pattern of use may be assessed regardless of whether you have overdue payments. NICE and KCB identify frequent use of cash advances as a negative factor.

Does checking my credit score often lower it?

KCB and NICE state in their disclosures that they do not use inquiry information in credit assessments. Credit inquiries should be distinguished from actually taking out a loan.

Do I get 30% of my debit card spending back in taxes?

30% is the income deduction rate for regular debit card spending, not a refund rate. The actual reduction in taxes depends on the deduction requirements and the result of your individual tax calculation.

Sources

Images

A woman takes a card from her wallet at a grocery checkout beside groceries and a payment terminal.
A woman takes a card from her wallet at a grocery checkout beside groceries and a payment terminal.
A man puts a credit card into his wallet beside a card statement at a kitchen table.
A man puts a credit card into his wallet beside a card statement at a kitchen table.