What does the DIY versus outsourced tax-bookkeeping calculator compare?
Self-bookkeeping avoids a monthly service invoice, but it uses owner or staff time to collect evidence, classify transactions, reconcile accounts, and prepare filings.
Outsourcing may reduce that workload, yet the monthly fee can exclude year-end closing, tax adjustment, income or corporate tax filing, payroll, extra locations, and cross-border work.
This calculator puts both choices on the same horizon, separates cash from internal time, and converts that time at an hourly opportunity value.
Costs often missed on the self-bookkeeping side
- Initial software setup and chart-of-accounts learning
- Monthly evidence collection, entries, and reconciliation
- Filing-season workload and occasional professional review
- Evidence-based expected cost of corrections or rebuilding records
Costs often missed on the outsourcing side
- Closing, adjustment, and annual filing fees outside the retainer
- Payroll headcount, additional location, or special-transaction charges
- Internal time for uploads, missing-item follow-up, and questions
- Rework or data recovery outside the written engagement scope
Korea-specific scope: results are in KRW and the legal notes use South Korean rules current on July 30, 2026.
The starting values are an illustrative formula check, not an official average, market benchmark, or recommended professional fee.
Build the inputs from records rather than memory
A useful break-even estimate begins with evidence.
Track two or three recent months in a calendar or time sheet, review accounting-software sessions and filing work, and then compare that record with a written outsourcing quote.
Using several months reduces the risk of treating a quiet month as normal while ignoring VAT, payroll, or annual closing peaks.
- Separate self-bookkeeping time. Track routine evidence work, month-end reconciliation, payroll and withholding, VAT, and annual income or corporate tax preparation.
- Choose an hourly-value basis. Use contribution margin the owner could realistically create, a replacement worker’s loaded cost, or the internal employee’s loaded compensation.
- Map the engagement line by line. Mark bookkeeping, VAT, withholding, payroll, social-insurance support, closing, tax adjustment, annual filing, locations, and headcount as included, extra, or excluded.
- Use one VAT basis. Compare both sides as VAT-inclusive or both as VAT-exclusive; mixing them can distort the apparent fee difference.
- Keep unsupported risk at zero. Enter an expected rework cost only when past frequency and actual cost, or a qualified review, provide a defensible basis.
The cost model
Self-bookkeeping economic cost
Cash cost includes setup cash, monthly software, annual filing or review support, and expected rework, prorated to the selected horizon.
Internal hours include initial learning, monthly processing, and annual filing work.
Self total = self cash + self hours × hourly value
Outsourcing economic cost
Cash cost includes onboarding, the monthly bookkeeping fee, annual closing or filing, contract add-ons, and expected rework.
Internal hours include monthly coordination and annual preparation that remain with the business.
Outsourcing total = outsourcing cash + internal coordination hours × hourly value
Input evidence for self-bookkeeping and outsourced bookkeeping costs| Cost layer | Self-bookkeeping | Outsourcing | Best evidence |
|---|
| Upfront | Training, setup cash, and hours | Migration and cleanup | Implementation quote and time log |
| Monthly | Software and processing time | Retainer and coordination time | Bills, calendar, and contract |
| Annual | Filing support and filing hours | Closing, adjustment, and filing | Prior-year invoice and quote |
| Rework | Expected correction or recovery | Out-of-scope remediation | Past cases and actual invoices |
Annual items are multiplied by comparison months divided by 12.
This linear proration supports partial-year comparisons, but it is not a prediction of the actual invoice date or payment schedule.
How to read the three break-even thresholds
1. Hourly-value break-even
Divide the cash-cost gap by the difference between self-bookkeeping hours and outsourcing coordination hours.
When self-bookkeeping uses more time, outsourcing becomes cheaper above the threshold; if self-bookkeeping uses less time, the direction can reverse.
Hourly threshold = (outsourcing cash − self cash) ÷ (self hours − outsourcing hours)
2. Monthly self-hours break-even
This threshold holds the hourly value and every cash item constant, then solves for monthly self-bookkeeping time.
Compare it with annual total hours divided by 12 rather than only a quiet month.
3. Monthly outsourcing-fee break-even
This is the monthly fee that makes total economic costs equal after onboarding, annual extras, rework, and internal coordination are already counted.
An actual quote below the threshold favors outsourcing on cost; a quote above it favors self-bookkeeping, subject to the non-cost checks below.
Why a finite threshold may not exist
Equal time means hourly value cannot change the ranking.
If outsourcing remains more expensive even when its monthly fee is zero, there is no non-negative monthly-fee threshold.
The calculator reports the direction instead of converting an economically meaningless negative threshold into a positive number.
Worked 12-month formula example
The following values are mathematical test inputs, not Korean market averages.
Use an hourly value of KRW 50,000, eight self-bookkeeping hours per month, one outsourcing coordination hour per month, KRW 20,000 monthly software, and a quoted KRW 150,000 monthly outsourcing fee.
Add ten setup hours and sixteen annual filing hours on the self side, four annual preparation hours on the outsourcing side, KRW 300,000 annual self review, and KRW 600,000 annual outsourced filing.
Twelve-month illustrative self-bookkeeping and outsourcing cost calculation| Result | Self-bookkeeping | Outsourcing |
|---|
| Cash cost | KRW 540,000 | KRW 2,400,000 |
| Internal hours | 122 hours | 16 hours |
| Time cost | KRW 6,100,000 | KRW 800,000 |
| Total economic cost | KRW 6,640,000 | KRW 3,200,000 |
Outsourcing is KRW 3,440,000 cheaper in this artificial example.
The hourly-value break-even is about KRW 17,547.17 per hour, the monthly self-hours break-even is about 2.2667 hours, and the monthly outsourcing-fee break-even is about KRW 436,666.67.
The large gap comes from 106 fewer internal hours, so the result is only credible if those hours can realistically be redeployed or valued at the chosen rate.
The 2026 Korean legal boundary
A lower economic cost does not change the legally required bookkeeping method.
The calculator does not determine simple-book eligibility, double-entry obligations, professional-business exceptions, verified-filing requirements, or tax-adjustment duties.
Individuals: Income Tax Act Article 160
Article 160 requires a business operator to keep evidence and record all business transactions so income can be determined, using double-entry bookkeeping as the general rule.
A smaller business that falls within the Presidential Decree and faithfully keeps the prescribed simple book is treated as having met the bookkeeping requirement.
The article-specific effective date verified through the National Law Information OPEN API was January 1, 2026, under Law ID 001565 and MST 280405.
Simple-book scope: Enforcement Decree Article 208
The current Article 208, effective July 1, 2026 under Law ID 003956 and MST 286211, describes the simple-book categories and required contents.
Paragraph 5 uses prior-tax-period revenue below KRW 300 million, KRW 150 million, or KRW 75 million for the three business groups, subject to exclusions, detailed industry classification, mixed-business conversion, and professional-business rules.
Those numbers appear here as a legal orientation only; this calculator does not turn them into an eligibility decision.
Corporations: Corporate Tax Act Article 112
Article 112 requires a corporation with tax liability to keep books using double-entry bookkeeping and retain important supporting evidence.
The verified article-specific effective date was January 1, 2026 under Law ID 001563 and MST 280349.
A corporation therefore compares internal capability with professional assistance inside a double-entry system; it should not reuse a simple sole-proprietor assumption without adjustment.
Tax-agent scope: Certified Tax Accountant Act Article 2
Article 2 lists representation for tax filings and claims, preparation of tax documents, bookkeeping for tax filings, tax advice, and related work within tax-agent services.
The current statute search returned Law ID 000639 and MST 280355; Article 2 itself was effective December 23, 2025, while the current consolidated statute includes provisions effective June 24, 2026.
Before outsourcing, verify registration, authority, the actual responsible professional, security controls, and the written scope; this calculator does not validate provider qualifications.
Books and evidence still require a retention process
Framework Act on National Taxes Article 85-3 requires books and supporting evidence to be retained, as a general rule, for five years after the statutory filing deadline for the relevant tax period and for seven years for offshore transactions.
The verified article-specific effective date was January 1, 2026 under Law ID 001586 and MST 280373.
Outsourcing does not remove the need for source-data delivery, review, backup, access control, and a contract-exit procedure for returning ledgers and files.
Practical business scenarios
Solo freelancer
A simple transaction pattern can still favor outsourcing when owner time has high contribution value. Strong automation and only one or two hours per month can instead favor self-bookkeeping.
Inventory-heavy business
Track purchases, payables, inventory, and VAT reconciliation separately. Confirm whether inventory or additional-location work creates a contract add-on.
Business with employees
Ask whether payroll, withholding, year-end settlement, and social-insurance support are included. Put joiners, leavers, and variable-pay work on the self side as well.
New corporation
Double-entry setup, corporate-card controls, shareholder and officer transactions, closing, and tax adjustment make setup hours and annual filing scope central. Do not copy a sole-proprietor example unchanged.
Engagement checklist before comparing quotes
Two quotes with the same monthly fee are not equivalent when their included services differ.
Mark each item as included, extra, or unavailable and move every extra into the annual add-on input.
Recurring work
- Monthly ledger entry and account reconciliation
- VAT and withholding filings
- Payroll, year-end settlement, and social-insurance support
- Monthly profit, receivable, payable, or inventory reports
Annual and exceptional work
- Closing and tax-adjustment statements
- Comprehensive income or corporate tax filing
- Amended filings, refund claims, or audit support
- Additional locations, employees, exports, or special transactions
Filing responsibility, submission deadlines, responsible-person changes, correction procedures, termination, ledger export, source-document return, and privacy or financial-data safeguards can matter as much as the fee.
A low retainer may produce a higher annual total when essential work is excluded.
Limits of the result
- The model adds nominal costs and does not discount cash flows or model inflation, after-tax hourly value, or invoice timing.
- It does not calculate expense deductibility or input-VAT recovery on professional fees; keep both options on one VAT basis.
- It does not invent tax savings, refunds, or avoided penalties from outsourcing. Model a separate scenario only with a documented amount.
- Annual fees and hours are prorated by months divided by 12. Adjust annual add-ons for minimum terms, termination charges, or lumpy filing invoices.
- The crossover month spreads annual items evenly and is an economic comparison, not a bank-balance or invoice-date forecast.
- When the cost gap is small, consider control of source data, reporting quality, absence coverage, privacy, and decision speed.
Frequently asked questions
Can I compare only the monthly bookkeeping fee?
Include annual closing, adjustment, income or corporate tax filing, payroll or location add-ons, and internal preparation time whenever the engagement prices them separately.
How should I set the owner’s hourly value?
Use realistic contribution margin or replacement labor cost. If bookkeeping time would not turn into revenue, run a conservative low-value case as well as a higher-value case.
Does the calculator apply Korean penalty rates to error risk?
No. Penalties depend on the filing failure, tax amount, timing, and other facts. Enter only a probability-weighted amount supported by past cases or a qualified review.
Does simple-book eligibility mean self-bookkeeping is cheaper?
No. The permitted bookkeeping method is a legal classification; economic cost depends on transaction volume, hourly value, internal capability, and the actual engagement scope.
Does outsourcing remove the need to retain records?
No. Maintain source-document, backup, access, review, and contract-exit procedures, including the format in which ledgers and files will be returned.
Should I accept a quote below the fee break-even immediately?
It is favorable on modeled cost, but still verify professional registration, included work, responsibility, security, correction, data return, and termination terms.
Official sources and update boundary
The Ministry of Government Legislation National Law Information OPEN API returned each source as current when checked on July 30, 2026.
These statutes support the legal boundary, not a statutory fee, market average, or universal processing time.
- Income Tax Act Article 160 — Law ID 001565, MST 280405, article effective January 1, 2026
- Income Tax Act Enforcement Decree Article 208 — Law ID 003956, MST 286211, article effective July 1, 2026
- Corporate Tax Act Article 112 — Law ID 001563, MST 280349, article effective January 1, 2026
- Certified Tax Accountant Act Article 2 — Law ID 000639, MST 280355
- Framework Act on National Taxes Article 85-3 — Law ID 001586, MST 280373, article effective January 1, 2026
Recalculate with this month’s actual records
Replace the illustrative amounts with time logs, software bills, and a written engagement quote to find the break-even boundary for your business.
Compare 12, 24, and 36 months to see whether upfront setup or long-run recurring cost drives the decision.