Start a business on the sideOn the side
Start for free
How it works

What a side business involves.
And what planix sorts out.

Every item for the UK – with the document it is in.

Every item with its document.

Start for free
What’s involved

planix sorts out 4 of 6 items.

You do the rest yourself.

Employment contract: side work allowed?ContractYou–
Offer, target customer, calculation per saleYour ideaplanixYour idea
Test: is there anything in the idea?Concept testplanixYour concept test
Sole trader or limited company, founding stepsLegal formplanixYour founding plan
Income Tax, National Insurance and VATTax and NIplanixYour founding plan
Self Assessment registration with HMRCHMRC registrationYou–

Sources: HM Revenue and Customs (HMRC): GOV.UK guidance ‘Tax-free allowances on property and trading income’ (HM Revenue and Customs (HMRC)), gov.uk, as of 06.04.2017 · HM Revenue and Customs (HMRC): GOV.UK guidance ‘Register for VAT’ (HM Revenue and Customs (HMRC)), gov.uk, as of 10.10.2024 · HM Revenue and Customs (HMRC): GOV.UK guidance ‘Self-employed National Insurance rates’ (HM Revenue and Customs (HMRC)), gov.uk, as of 06.04.2026

The path

Handing in your notice comes last.

Five steps – registering with HMRC is required, quitting is not.

  1. FirstRead your contract

    What your employment contract says about side work – before your first customer.

    What your contract says.

  2. With planixSharpen the idea

    What you sell to whom – with the time and budget you have next to your job.

    With your time and budget.

  3. With planixTest

    A concept test shows whether there is anything in it before you invest money.

    Before you invest.

  4. RequiredRegister with HMRC

    Self Assessment once your side income passes £1,000 a year – by 5 October after that tax year.

    Self Assessment with HMRC.

  5. LaterGrow

    Your job stays until your business carries you. You choose the moment.

    Job stays until it carries.

Your profit is added to your salary and taxed at your highest Income Tax band – in Scotland at the Scottish rates.

Result

Three documents. One venture.

Each module takes over what you entered before.

Develop the ideafree

Your idea

Web · PDF · Word

Your idea on one page – and as a Business Model Canvas.

  1. 1At a glance
  2. 2Value proposition and target customer
  3. 3Problem and differentiation
  4. 4Business model
  5. 5Business Model Canvas
  6. 6What is still open

Plus the canvas as a Word file.

Start Develop the idea
Test your ideafree

Your concept test

Web · PDF

What 10 simulated respondents say about your idea.

  1. 1Starting point
  2. 2Result of the concept test
  3. 3Scope and assumptions
  4. 4Questions for real conversations
  5. 5Your next steps

Simulated respondents are marked as such.

Start for free
Start a businessfree

Your founding plan

Web · PDF · Word

Legal form, registration and obligations – for your side business.

  1. 1At a glance
  2. 2Legal form
  3. 3Founding roadmap
  4. 4Tax and accounting
  5. 5National Insurance and staff
  6. 6Your next steps

Every number with authority and source.

Start now
Afterwards

Seamlessly on in the founder journey.

What you enter stays in your account. Business plan and first customers build on it.

Everything stays in your account.

  1. IdeaFind your business idea · Develop the idea
  2. ValidationTest the idea · Test the market
  3. PlanningBusiness concept, business plan, funding
  4. FoundingFound and protect your company
  5. GrowthGo-to-market · Investors · Scaling

View the whole founder journey

Supported by start-up experts and partners

NVIDIA Inception Program
REP27 – EU & UK GDPR Representative
collumino.com
STARTUPS

Start on the side?
Begin tonight.

The idea first. Test and registration when you’re ready.

Start for free All three modules free · no subscription