Systems & Network Engineer Tax Guide

Q: Should travel allowances I receive from client companies be included in my reported revenue?

If the reimbursement clearly has the character of an out-of-pocket expense refund and there's documentation, there are cases where it can be treated separately from revenue, so it's worth reviewing your contract structure and payment method together.

Q: I have maintenance contracts with several companies — do I need to register a business?

If you're providing services on an ongoing, repeated basis, business registration is the standard approach, and depending on your revenue scale you can choose between simplified and general taxation, whichever is more advantageous.

An engineer who keeps a company's server hardware and network infrastructure running smoothly. Guidance tailored to your field, from income structure to expense processing and tax-saving points.

You're always on the road between client sites — let us handle the vehicle-expense math

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I drive my own car between multiple client sites — how much can I claim in vehicle expenses?

If you're a simplified-bookkeeping filer due to smaller revenue, you can allocate fuel, insurance, and auto tax by your business-use ratio and reflect them as necessary expenses, but once your revenue grows and you become a double-entry bookkeeping obligor, the special rules for business-use vehicles apply — depreciation is capped at 8 million KRW a year, and the overall cap including fuel and insurance is 15 million KRW a year. Keeping a driving log lets you claim the business-use portion with no cap, and it's also important to check whether you need business-use-only auto insurance based on your revenue scale.

Income Structure Features for Systems & Network Engineers

A representative role with a very high proportion of on-site client work

Recurring service contracts in the form of maintenance agreements (MA) are common

Night and weekend on-call response allowances are often included in income

Key Necessary Expense Items

Certification acquisition and renewal costs — Engineer Information Processing, Network Administrator, and more

Personally owned diagnostic equipment and tools, plus consumables like cables and adapters

Remote monitoring tool subscriptions

Vehicle fuel, insurance, auto tax, and repair costs allocated by business-use ratio

Phone bills for night on-call standby

Tax Advantages for Systems & Network Engineers

Reviewing disguised-subcontracting risk in recurring maintenance contracts

We tighten up your contract language against your actual working reality to manage labor risk.

Tax-saving design using revenue stability

We use the stable income from multi-year contracts as the basis for the Nolan Umbrella Fund and pension savings.

Clarifying the split between travel allowances and reimbursements

We separate out-of-pocket reimbursements from revenue to prevent double taxation.

The Most Common Mistake in the Field

Some people with maintenance contracts at multiple companies, making regular site visits, report their travel and transportation reimbursements as part of revenue rather than separately, ending up paying unnecessary extra tax.

Frequently Asked Questions

Should travel allowances I receive from client companies be included in my reported revenue?

I have maintenance contracts with several companies — do I need to register a business?

I use my own car to visit sites — how much of the vehicle cost can I claim as an expense?

If you're a simplified-bookkeeping filer due to smaller revenue, you can allocate fuel, insurance, and auto tax by your business-use ratio and reflect it as a necessary expense. But once your revenue grows and you become a double-entry bookkeeping obligor, the special rules for business-use vehicles apply (a cap of 15 million KRW a year, uncapped if you keep a driving log), and business-use-only auto insurance also becomes necessary — so the rules change based on your revenue scale.

Related Roles Worth a Look

Cloud & DevOps Engineer

An engineer who builds cloud environments like AWS and Azure and automates development and deployment

Security Engineer

An engineer who audits systems for vulnerabilities and builds defenses against attacks and data encryption

Database Administrator (DBA)

A specialist responsible for database design, operation, performance tuning, and security

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