AI Agent Side Jobs: Work Rules, Contracts and Taxes to Check First

An AI agent side job does not end with selling what you build. It involves your relationship with your employer, your contract with the client, the terms of the tools you use, and reporting your income. This article lists, in order, what employees who want to start building or selling AI agents on the side should check.

The rules and terms in this article were checked in October 2026 against Japan's Ministry of Health, Labour and Welfare, Japan's National Tax Agency, e-Gov Law Search (Japan's official legal database) and each tool's official pages. For decisions about your own case, check with your employer's responsible department, your tax office or a professional.

Forms of side work: client work, selling, publishing templates

AI development side work falls into three broad forms. The form changes your relationship with the other party and the rules you need to check.

• Client work: take requests from a company, then build, configure and maintain AI agents or workflows for it
• Selling: sell AI agents or AI apps you built yourself, as a one-time purchase or a monthly plan
• Publishing templates: publish n8n or Dify workflows as templates

Side work with n8n or Dify fits into these three forms. For example, building an internal AI app in Dify and delivering it into the client's environment is client work. Letting several companies use the same system is selling. For AI app side work in general, the form depends on whose environment runs it and who maintains it.

If you are starting as an individual developer, choosing one form first narrows your preparation. Client work centers on a contract with each client. Selling centers on what the sales page shows and how you deliver. The differences between sales methods are covered in How to sell an AI agent you built.

Your employer's work rules and the side job guidelines

The first thing to check is your employer's rules. The “Guidelines for Promoting Side Jobs and Multiple Jobs” from Japan's Ministry of Health, Labour and Welfare (MHLW) ask workers who want a side job to first check their employer's rules on side jobs (employment contract, work rules and so on).

Based on court cases, the same guidelines list examples of when a company may restrict side jobs.

• When it interferes with the work the employee provides
• When business secrets would leak
• When competition would harm the company's interests
• When the conduct damages the company's reputation or credibility, or destroys the relationship of trust

In AI agent side work, pay special attention to secrets and competition. Do not put customer information or internal data you learned at your main job into your side-job AI. If you take client work from a company in the same field as your main job, first check that it does not count as competition. If your company has a notification or approval process, submit it with a concrete description of the side work.

The guidelines also state that working as a freelancer or running your own business is not subject to combining working hours. However, they ask you to manage your own working time and health so that overwork does not affect your main job.

What to set in the contract for client work

For client work, agree on the terms in writing with the client before you start. Settle the following points.

• What you build: the target task, the scope handed to AI, and the scope a person checks
• Fee: amount, payment due date, and how extra work is handled
• Delivery and acceptance: what you deliver, when and how, and what counts as complete
• Where it runs and whose accounts: whose server and whose AI model account are used
• Maintenance: how far you respond to defects after delivery and changes in connected services
• Rights to data and deliverables: how entrusted data is handled, and who holds rights to what you build

When an individual with no employees takes work from a business, the Act on Ensuring Proper Transactions Involving Specified Entrusted Business Operators (Japan's Freelance Act) applies. Article 3 of this act requires the ordering business to state the details of the work, the fee, the payment due date and other terms in writing or by electronic means. Article 4 requires ordering businesses that have employees, among others, to set the payment due date as short as possible within 60 days from the day they receive the work.

Keep emails and purchase orders that state the terms. How to set the contract is covered in How to run AI agent development projects.

Check the licenses of the tools you use

If your side work uses n8n or Dify, check the tool's license. The terms for running it on your own server are as follows.

The n8n License FAQ also gives a contact for unclear cases. If you cannot tell which side your sales method falls on, check before you sell. The conditions for using n8n commercially are also covered in n8n commercial use. AI model APIs are also subject to their own terms of use.

Tax filing and income categories

In Japan, side-job income is classified by its nature, for example as business income or miscellaneous income. The National Tax Agency's Tax Answer lists side-job income as an example of miscellaneous income, and treats side-job revenue earned continuously for profit as “miscellaneous income from business activities”.

Whether income counts as business income depends on whether the activity is carried out on a scale generally regarded as a business. The Basic Circular on the Income Tax Act states that if no books recording transactions are kept, the income is miscellaneous income from business activities. The exception is when revenue exceeds ¥3 million and there are facts supporting business income.

Whether you must file a final tax return depends on the amount of income. If you receive salary from one employer and all of it is subject to withholding, you must file when your total income other than salary and retirement income exceeds ¥200,000. Income here means revenue minus necessary expenses.

Miscellaneous income from business activities has other rules too. If that revenue two years earlier exceeded ¥3 million, you must keep records of cash and deposit transactions. If it exceeded ¥10 million, you must attach a statement of income and expenses or similar documents when you file your return. A loss in miscellaneous income cannot be offset against other income such as salary. Check resident tax (local inhabitant tax) procedures with the municipality where you live.

Whichever category applies, keep records of sales and expenses. Also keep receipts for costs paid for the side work, such as AI model usage fees and server costs.

Steps for listing on Employee Store

If you choose to sell, you can also list on a marketplace. Employee Store is a marketplace where companies can adopt AI agents (AI employees) built by developers as a one-time purchase, a monthly plan, or an upfront fee plus a monthly plan. Any format is accepted, including n8n or Dify workflows and agents you developed yourself.

After you list, the operations team reviews it, usually within 3 business days. There is no listing fee and no upfront cost. The commission is 20% of the deal amount and applies only when a deal closes. Delivery is due within 3 business days in principle, and the buyer is refunded if it is late. Sales become available for payout after the buyer confirms receipt, or 14 days after delivery. You can request a payout from ¥500 under “Sales and payouts” in My Page. Employee Store Operations sends the transfer manually, and it usually arrives within 5 business days. Bank transfer and remittance fees are deducted from the payout amount.

Sales from listings are also side-job income subject to reporting. Keep payout records together with your sales records. One person can list several AIs, and Employee Store is looking for early listing partners. See the seller guide for the terms.