Why Your Next Side Project Might Be a Tax Tool—and How to Tap into It

You might be surprised, but hear me out: building or using a tax-calculation tool can be a game-changer—both for productivity and for gaining smarter insights into your finances. I used to think tax tools were all boring maths and legal headaches, but I discovered they can have real value, especially if you’re a freelancer, run a side hustle, or just want to be more in control of your money. Let’s walk through why this matters and how you (yes, you) can turn it into something useful.

The smart reason behind tax calculators

Think about this: you’re working on a passion project. You’ve got income coming in, maybe expenses going out. You know you’ll owe some tax at the end of the year, but you don’t want that looming surprise. That’s where a tool designed to estimate your tax liability steps in.
 Why it’s smart:

• It gives you visibility—you see the likely cost ahead of time rather than waiting until a shock.
  
  
• It helps with planning—if you know you’ll owe a certain amount, you can prep instead of scrambling.
  
  
• It builds confidence—you’re not blindly hoping you’re “okay,” you know where you stand.
  
  

Imagine you’re working evenings on a side gig, you get some income, but you’re also spending (equipment, software, maybe travel). A tax-calculator lets you plug in “okay, I made £ X, spent £ Y, how much might I owe?” Suddenly you’re not flying blind.

Choosing the right tax tool

Not all calculators are created equal. Some are simple, others get more complex. What should you look for?

• Ease of use: If a tool requires a PhD to input your data, you’re less likely to use it.
  
  
• Relevant to your jurisdiction: If you’re in the UK (or dealing with UK income) you’ll want something tailored.
  
  
• Expense support: It should let you track your business‐type expenses (if applicable) so your tax estimate is more realistic.
  
  
• What-if scenarios: “What if I earn more?” “What if I spend more?” Good tools let you play around.
  
  

One example worth checking out is itaxcalc.co.uk. It offers a UK-based platform that helps estimate your tax liability for side income, freelancing, or small business activity. I’ve played around with it and found it gives a practical snapshot rather than abstract numbers—so you can make real decisions.

How I used it (and what I learned)

I’ll get personal for a minute: in one quarter I had income from a small freelance gig. I wasn’t sure how much tax I’d owe, I was also spending on gear and software, and I didn’t want to get burned by an unexpected bill. So I used a calculator like the one above.

What happened:

• I entered my estimated income and typical expenses.
  
  
• I got a tax estimate that said, “roughly this much you owe if things hold.”
  
  
• That number made me set aside a portion of my income in a separate savings pot—so when tax season hit I wasn’t scrambling.
  
  
• I also used the number to decide: “Should I invest more in my side hustle this quarter? If my net after tax is going to be X, maybe yes, maybe no.”
  
  

The result? I felt more in control. Instead of being surprised by a tax bill, I already had a plan. And I didn’t have to reduce all my fun or creativity—just had a smarter budget.

Turning it into a habit

Alright, here’s the fun part: making this sticky—not just a one-time check but an ongoing habit. Because the real benefit comes when you stay ahead.

1. Monthly check-in – At the end of each month, input your income and expenses into the calculator. This keeps you updated.
   
   
2. Set aside automatically – Decide: “If I owe roughly £ X, I’ll set aside Y% of income.” Automate if you can.
   
   
3. Review before major decisions – Thinking about buying new gear, expanding? Run the scenario: “If my income goes up by 20%, what happens to tax?”
   
   
4. Year-end prep – As the tax year ends, you’re not scrambling. You already have a forecast.
   
   
5. Reflect and adjust – Did your estimate match actual? If not, ask: why? Then adjust your model and assumptions.
   
   

Why it matters beyond taxes

Here’s the kicker: It’s not just about taxes. Using a tool like this is a small skillset but multiplies in value. Because now you’re:

• Thinking like a business – Even if you’re a freelancer or side-hustler, you’re adopting a mindset of “how much do I net?” not just “how much did I earn?”.
  
  
• Reducing anxiety – Money and taxes cause stress. When you have visibility, it’s less scary.
  
  
• Empowering decisions – When you know the cost, you can choose: Do I invest more? Do I pause? Do I change strategy?
  
  
• Building data for the future – Over time, you’ll have historical estimates. Then you can spot patterns: “Okay, Q2 is always lean” or “Expenses spike when I do X”.
  
  

Common mistakes (so you can avoid them)

Since I’ve stumbled on a few of these, I’ll share so you don’t repeat them:

• Using generic tools that aren’t tailored – If you use a US-based calculator but you’re in the UK, you’ll get misleading numbers. Always pick your local rules.
  
  
• Ignoring expenses – If you only enter income, you’ll vastly over-estimate tax. Expenses matter.
  
  
• Treating the estimate as final – It’s an estimate. Real tax might be slightly more or less. Use it for planning, not for mental panic.
  
  
• Doing it once and forgetting – If you only plug in numbers once, you’ll lose relevance and surprise may creep back.
  
  
• Under-saving – If you calculate you’ll owe £ 1,000 and you set aside £ 300, that’s a warning sign. Set aside enough to cover if things go a bit worse.
  
  

Why this mindset fits the nerdbot mindset

I think this topic fits the whole “nerd” spirit of previewing, planning, understanding systems. We love dashboards, we love metrics, we love knowing how things tick. A tax estimator is less glamorous than a new gadget but it’s the same energy: you’re pulling back the curtain, you’re seeing the guts of the system. It’s part of leveling up.

Also: many of us in tech, freelancing, side-projects, or startup life are doing everything ourselves. One moment you’re coding, the next you’re invoicing, the next you’re scratching your head at tax. Tools like this bridge the gap, reduce friction, let you focus on the creative work, not the panic.

Your next steps (yes, you)

So here are your action steps to make this real:

• Visit https://itaxcalc.co.uk/ and plug in a rough guess for your income and expenses for the past month.
  
  
• Decide on a tax-set-aside percentage (for instance, start with 20%) and schedule an automatic transfer into a “tax pot”.
  
  
• At the end of this month, revisit the calculator with updated numbers and see how your estimate changes.
  
  
• Before you commit to any big expense (gear, software, hire), do a “what if income goes up/down” check.
  
  
• At year end, compare your estimated tax vs actual and note what assumptions were off so you improve next year.
  
  

You’ve got the power to transform your approach—not just by working harder, but by working smarter. A small shift in how you handle your side income and tax planning can free your mental space, reduce risk, and help you stay focused on what you love doing. It’s not about being a tax expert—it’s about being in control. And that’s way more fun.

Hit me if you want a walk-through of how I use such a tool month-to-month with real numbers (anonymised, of course). We’ll make it nerd-friendly and totally doable.