Saving for a Goal One Year Out: Why the Lump Sum and the Monthly Amount Belong in Different Products
Saving for something a year away, most people reach for an installment savings account. It is the product built for monthly contributions, so the instinct is sound. It stops being sound the moment you already hold a lump sum. Trying to solve both halves with one product quietly costs money. A wedding fund makes a convenient worked example.
Money you already have belongs in a time deposit. Money you will add monthly belongs in an installment savings account. Savings accounts are built around monthly contributions and will not accept a lump sum, and even where they do, late money sits for too little time to earn much. On a plan of KRW 10,000,000 already saved plus KRW 1,000,000 a month for a year, whether the lump sum sits idle or in a time deposit is worth KRW 380,700 after tax.
The two halves need different products
The difference is how long the money is actually on deposit. A time deposit takes the whole amount at the start and holds it to maturity, so the full principal earns for the entire term.
An installment savings account works the other way. The first contribution sits for twelve months, the last for one. Averaged across the term, contributed money is on deposit for roughly half the period. That is why the same headline rate produces far less interest on a savings account, and why savings rates are quoted higher in the first place.
The mistake follows naturally. The savings rate looks better, so people try to push the lump sum into it too. Most savings products cap monthly contributions and will not take a lump sum at all, and where money does go in late it earns almost nothing.
What the split is worth
Take KRW 10,000,000 already saved and KRW 1,000,000 added monthly for twelve months. Total contributions reach KRW 22,000,000.
In the 2026-07 disclosure, among 12-month products openable without a branch visit, the best installment savings rate is 8% at 애큐온저축은행 (처음만난적금), and the best time deposit rate is 4.5% at 엔에이치저축은행 (NH특판정기예금(모바일)).
| Allocation | After-tax interest | Total after one year |
|---|---|---|
| Lump sum left in a current account, monthly contributions only | KRW 439,920 | KRW 439,920 |
| Lump sum in a time deposit, monthly contributions in a savings account | KRW 439,920 + KRW 380,700 | KRW 820,620 |
| Same split, but no preferential conditions met on the savings account | KRW 357,435 + KRW 380,700 | KRW 738,135 |
Simple interest with the 15.4% interest income tax applied. Installment savings assumes fixed monthly contributions over twelve months; the time deposit assumes payment at maturity. High-rate savings products often cap monthly contributions, so the full KRW 1,000,000 may not be permitted.
The gap between the first row and the second is KRW 380,700. The only difference in behaviour is opening one additional account.
The third row matters too. Meeting none of the savings account’s preferential conditions drops it to its 6.5% base rate, at which point the time deposit contributes more interest than the savings account does. Choosing a savings product on its maximum rate alone is how that happens.
Why headline rates mislead here
In the calculation above the savings rate was 8% and the deposit rate 4.5%. On those numbers the savings account looks far superior. Expressed as a return on money actually paid in, the order reverses.
| Product | Headline rate | Total paid in | Pre-tax interest | Return on money paid in |
|---|---|---|---|---|
| Installment savings, 12 months | 8% | KRW 12,000,000 | KRW 520,000 | 4.33% |
| Time deposit, 12 months | 4.5% | KRW 10,000,000 | KRW 450,000 | 4.50% |
Simple interest, before tax. The savings figure assumes KRW 1,000,000 monthly for twelve months; the deposit figure assumes KRW 10,000,000 placed once.
A 8% savings account returns 4.33% on contributions. A 4.5% time deposit returns 4.50%. The savings rate is nearly double and still finishes behind.
None of which makes savings accounts bad. Building money you do not yet have is exactly what they are for, and nothing else does it. The point is narrower: using a savings account to hold money you already have is a losing trade. Comparing the two products head to head was the wrong comparison from the start.
If the horizon is not twelve months
Weddings land at six months or two years just as often. Rates differ by term.
| Term | Best time deposit | Best installment savings |
|---|---|---|
| 6 months | 4.4% | 6.5% |
| 12 months | 4.5% | 14% |
| 24 months | 4.25% | 8% |
2026-07 disclosure, before tax, highest maximum rate among products openable without a branch visit. Actual rates depend on meeting preferential conditions.
Longer does not automatically mean better. Promotional pricing sometimes puts shorter terms ahead. Stretching the term to chase a rate is usually worse than matching the date you actually need the money.
Allow for the date moving
Wedding timelines slip. Setting maturity exactly on the date you need the funds means any acceleration forces an early termination, and early termination replaces the contracted rate with a much lower one.
Two adjustments help. First, set maturity slightly before the date you need the money. Sitting in a current account for a few days costs almost nothing; breaking a deposit costs the interest.
Second, do not commit the entire amount to one product. Money that goes out early, such as deposits and booking fees, belongs somewhere accessible. Only the final payment needs locking away.
While you are saving
Contribution ceilings
The higher the rate, the tighter the monthly cap tends to be. If you plan to contribute KRW 1,000,000 a month, confirm the product permits it. Splitting across two products is a workable answer.
Contribution dates
Setting the debit for the day after payday avoids failed transfers. Missing a contribution can break a preferential condition or push back maturity, depending on the product.
Protection ceiling
At around KRW 22,000,000 the whole plan sits inside the deposit protection ceiling, so a single institution is fine. Splitting becomes relevant as the total approaches the limit.
TIP. If two people are saving together, holding the products in separate names is often better. First-time customer conditions and one-account-per-person rules apply to each of you, and the protection ceiling is assessed per person.
Frequently asked questions
Can I put a lump sum into a Korean installment savings account?
Generally not. These products are built for monthly contributions and cap the monthly amount. Money paid in late sits for too short a period to earn meaningful interest. A time deposit is the right home for a lump sum.
For a one-year goal, is a deposit or a savings account better?
It is not a choice between them. Money you already hold goes into a time deposit; money you will add goes into a savings account. On KRW 10,000,000 the difference between leaving it idle and placing it on deposit is KRW 380,700 after tax.
Why does a higher savings rate produce less interest?
Because contributed money is on deposit for about half the term on average, whereas a time deposit holds the full principal throughout. At the same rate, a savings account pays less.
What if the date moves?
Set maturity slightly before the date you need the funds. Money can sit in a current account for a few days at little cost, but terminating early replaces the contracted rate with a much lower one.
Should a couple combine or separate the accounts?
Separating is usually better. First-time customer conditions and one-account rules apply per person, and the deposit protection ceiling is assessed per person as well.