Last reviewed: 30 May 2026
Quick summary
- You build custom GPTs, AI assistants or workflow templates for clients and need to decide whether the income is service work, digital products or both.
- Record client service fees and template sales separately, before AI tool costs and platform fees.
- The useful accountant conversation is about evidence: client scopes, GPT or assistant setup invoices, template marketplace reports.
Topic hub: Side hustle tax hub
Direct answer
If this activity is organised to make money, the tax question is not whether it started from influencer advice. It is whether you have taxable trading income, what your gross income is for the tax year, what evidence supports your costs and whether Self Assessment, VAT or MTD need checking. For this page, focus on client service fees and template sales separately, before AI tool costs and platform fees.
How money actually arrives in this niche
People in this niche rarely think in neat accounting words. They think in custom build fees, training sessions, maintenance retainers, template sales, support packages and referral commission. That is why a generic side-hustle calculator is not enough. You may see a payout, a dashboard, a retainer, a free product, a credit balance or a Stripe transfer and assume that is the tax number. It often is not.
The practical starting point is to list each income stream in the language of the platform or client. Then translate it into accounting records: gross income, refunds, platform fees, contractor costs, software costs and any non-cash value connected to work. This makes the page useful before an accountant call because the reader can send a clean summary rather than a folder of screenshots.
What figure should you record?
Record client service fees and template sales separately, before AI tool costs and platform fees. Keep the gross figure visible even if the platform pays out a smaller amount. If a client or platform deducts fees before money reaches your bank, the bank deposit may be a poor shortcut. If you receive products, credits, samples, usage rights or commission, keep those notes with the same discipline as cash receipts.
For the trading allowance, GOV.UK refers to gross trading income. That means you should understand the gross figure before deciding whether the trading allowance or actual expenses is more useful. If the activity grows, the same gross-income habit also helps with VAT and MTD checks.
Records to gather
For this exact niche, collect these before filing or speaking to an accountant:
- client scopes
- GPT or assistant setup invoices
- template marketplace reports
- AI tool invoices
- support retainer records
Add a one-line note explaining what each cost was for. A receipt called "subscription" is less useful than "ChatGPT Team for client chatbot builds, May 2026". That small habit is the difference between an accountant giving quick guidance and spending time reconstructing the story.
Real examples
- You charge GBP 350 to build a custom GPT for a recruiter. Keep the scope and invoice.
- You sell a reusable template for GBP 29. Track that separately from client consulting.
- A client pays monthly for updates. Record the retainer even if no major work is done that month.
Mistakes to avoid
- Mixing consulting and template sales with no category split.
- Not keeping client scopes for custom builds.
- Ignoring support retainers because they feel small.
- Claiming broad AI subscriptions without business-use notes.
What this guide is focusing on
Use this guide if you are a small-business owner trying to pin down the next practical tax or records decision before speaking to anyone. For Custom GPT builder tax UK: selling GPTs, templates and automation setups, focus on how the rule meets the records, thresholds, software and decisions you actually have in front of you.
What figure, record or decision should you pin down?
Pin down income source, dates, records quality, deadlines, thresholds, software, and whether the issue is simple admin or a judgement call. That gives an accountant something specific to check and stops the conversation becoming a vague discussion about tax in general.
Records to gather
- income totals
- expense categories
- software exports
- HMRC letters
- deadline dates
Real examples for this situation
- A tidy sole trader may be able to file alone, while a growing business with VAT or MTD worries needs a clearer system.
- A missed deadline is different from a pricing decision, even though both may need an accountant conversation.
- A structure decision should use expected future income rather than last year's figures alone.
A common mistake is asking for advice before gathering the figures that decide the answer. The safest pattern is to write down the figure, source, date and evidence before deciding whether DIY, software or accountant support is enough.
Questions to ask an accountant
- Is this service income, product income or both?
- Should templates and client builds be tracked separately?
- Can I claim AI tools and hosting?
- Do I need terms for client data and support?
- When would VAT or a limited company be worth discussing?
Send the questions with your totals. A useful accountant call starts with the money model, not just the job title.
Official guidance checked on 30 May 2026
Rules and thresholds can change. These GOV.UK sources were checked during this rewrite and should be rechecked before important filing decisions.
Related guides and tools
FAQs
What figure should I record?
client service fees and template sales separately, before AI tool costs and platform fees
What records should I keep?
client scopes, GPT or assistant setup invoices, template marketplace reports, AI tool invoices, support retainer records.
When should I speak to an accountant?
Speak to an accountant if the activity is regular, crosses a reporting threshold, involves VAT, MTD, gifted products, foreign currency, contractors, company structure or a tax return you are not confident filing.