Tax-Saving Strategies for Developers

If You Don't Understand Taxes, Earning More Won't Help

A developer earning 70 million won (roughly $54,000) a year has an effective tax rate of about 15-17%.

When you add up income tax, local income tax, and the four major social insurance premiums (Korea's mandatory national health insurance, pension, employment insurance, and industrial accident insurance), you're paying over 12 million won per year. That's a million won every month going to taxes, yet surprisingly few developers make a concrete effort to reduce that number.

The way I see it, tax optimization is the second most effective way to increase your real income, right after salary negotiation. Getting a 5-million-won raise is hard, but getting 2-3 million won back through tax savings is something you can start doing right now.

What Salaried Developers Keep Missing

Let's start with the most commonly overlooked items in year-end tax settlements (Korea's annual tax adjustment process where employees can claim deductions and credits).

Education expenses. Job-related education costs are eligible for tax credits up to 3 million won per year. Online courses from Udemy, Coursera, and Inflearn (a popular Korean learning platform) all qualify.

Technical book purchases count too. But most developers never bother saving those receipts. For overseas course platforms in particular, you need to organize your payment records separately.

Charitable donation deductions are surprisingly useful as well. Donations to open-source foundations like Apache or the Linux Foundation are eligible for tax credits.

You can deduct donations up to 30% of your annual income — contributing to open source while reducing your taxes is a genuine two-for-one deal.

Personal pension plans and IRPs (Individual Retirement Pensions) are table stakes.

Put 9 million won into an IRP and you can get back up to 1.485 million won. With an annual income of 70 million won, the 13.2% tax credit rate applies. That's effectively a guaranteed 16.5% return on your contribution. No stock investment can promise you 16.5% annually with that kind of certainty.

Freelance and Side Project Income

From personal experience, once side project income starts coming in, the tax situation gets complicated.

If you have freelance income while employed full-time, you need to file a comprehensive income tax return in May. Your employment income and business income get combined, which can push you into a higher tax bracket.

With 70 million in salary plus 20 million in business income, you're looking at a 35% tax rate on the combined 90 million won. The rate bracket jumps significantly.

But business income allows you to claim necessary expenses.

Equipment purchases (MacBook, monitors, keyboards), software subscriptions, internet costs, coworking space fees, and cloud service expenses can all be written off as business costs. Claim these properly and your tax bill drops considerably.

Choosing between the simplified expense rate and standard expense rate matters too. If your annual revenue is under 24 million won, the simplified rate lets you write off about 64% of your revenue as expenses. In that case, the actual tax bill is quite small.

What People Say vs. What Actually Happens

People say "just hire an accountant and they'll handle everything," but in reality, an accountant can't optimize your taxes without understanding your specific situation.

Not many accountants understand the peculiarities of being a developer. Is a GitHub Copilot subscription a work expense? Does a personal AWS account count as a business cost? Is an overseas conference fee considered education? You need to sort these out yourself and present them clearly.

If you just hand over a stack of receipts, the accountant will process them conservatively — safely, sure, but you'll get less money back.

What I recommend is keeping a spreadsheet that separates your expenses into "work-related" and "personal" categories throughout the year. Ten minutes a month can save you hundreds of thousands of won at tax time.

The Option of Incorporating

Once side project revenue exceeds 40-50 million won per year, it's worth considering setting up a one-person corporation.

The top personal income tax rate is 45%, while the corporate tax rate for income under 200 million won is just 9%.

The gap is enormous. Of course, if you pay yourself a salary from the corporation, income tax kicks in again. But by adjusting your salary level and keeping profits inside the corporation, you can reduce your overall tax burden.

Paying attention to taxes is tedious, but the payoff for that tedium is millions of won per year. It's an optimization every bit as worthwhile as refactoring your code.