From Paycheck to Prosperity: How a Simple % Percentage-Based Budget Transformed My Finances

As a urology registrar working in Queen Alexandra Hospital Portsmouth (for more years than most), I know how demanding our jobs are. Most of my colleagues pay for direct debits once payday comes, pay off their spending through a credit card as much as they can, then save an invest the rest, if there is any left! But what if I told you there's a simple, yet powerful way to take control of your money and build a secure financial future? It all starts with thinking in percentages.

I remember when I first started my career as a foundation year doctor. My finances were a mess. I was living paycheck to paycheck, and I had no idea where my money was going. It wasn't until I sat down when I was a surgical SHO in my FY3 year and created a budget based on percentages that I finally felt like I was in control. When I was in my CST years a couple of years later, I realised this planning process was, and still is, a game-changer for me.

And I'm not alone. The UK household saving ratio has been on a roller-coaster ride, recently dropping to 9.5% in the third quarter of 2025 [1]. This means people are saving less of their disposable income. It's a worrying trend, but it also highlights the importance of taking control of your finances.

The 28-15-20 Rule: Your Starting Point

Let's start with a simple rule of thumb: the 28-15-20 rule. This isn't a strict law, but rather a guide to help you get started. Here's how it works:

• 28% for your mortgage or rent: This is your biggest fixed cost, so it's important to keep it in check. Don’t become ‘House-Poor’ by buying a house are about to buy, but realistically cannot afford. There is a difference between what you can buy and what you can afford. I have some content on this coming up shortly.

• 15% for your car: This includes your car payment, insurance, and fuel. I know, it’s not a lot. But seriously cars are one of the most depreciating-in-value things you can buy on this planet. Don’t fork out large amount of your monthly pay for a fancy car, trust me, you would be surprised how little people really care about what car you drive, they got their own problems to think about.

• 20% for investing: This is the magic number that will help you build wealth over time. Pay yourself first! You will see coming up, as your pay increases, this 20% does not change, it will go up, but the investing portion monthly will never drop below 20%. Non-negotiable!

Now, let's see how this plays out in real life with a hypothetical example.

Year 1: Setting the Foundation

In our first year, let's say your monthly take-home pay is £2500. Using the 28-15-20 rule as a guide, your finances might look something like this:

•       Mortgage: £700 (28%)

•       Car: £375 (15%)

•       Investing: £500 (20%)

•       Spending: £925 (37%)

Notice that your spending is what's left over after you've paid your fixed costs and invested. This is a crucial mindset shift. Instead of spending first and saving what's left, you're prioritizing your financial future.

Year 3: The Power of Fixed Costs

Fast forward two years, and you've gotten a pay rise! Your monthly take-home pay is now £3500. Here's where the magic of percentages really starts to shine.

Your mortgage and car payments are fixed costs. You still owe the same amount each month, but as a percentage of your higher salary, they've shrunk:

•       Mortgage: £700 (from 28% to now 20% of your salary)

•       Car: £375 (from 15% to now 10.7% of your salary)

Because you've kept your investment percentage at a constant 20% (non-negotiable!!), you're now investing more money each month:

•       Investing: £700, 20% of £3500 (from £500/month in year 1 to £700/month)

And the best part? Your discretionary spending has also gone up!

•       Spending: £1725 (49.3%) (from £500/month in year 1 to £1725/month)

This is the beauty of controlling your fixed costs and prioritizing investing. As your income grows, you can enjoy a better lifestyle while still building your wealth.

Year 5: Accelerating Your Wealth

Five years in, and you're earning £5000 a month. Your fixed costs are now an even smaller portion of your income:

•       Mortgage: £700 (from 28% dropped to 14%)

•       Car: £375 (from 15% dropped to 7.5%)

Your investment contribution has doubled since year 1:

•       Investing: £1000 – 20% as constant through the years (used to be £500/month)

And your spending money has continued to grow:

•       Spending: £2925 (58.5%)

At this point, you might even ask yourself, "Could I be investing more?" This is a great question to ask! As your financial situation improves, you can start to be more aggressive with your investments. Go through you spending costs, especially the small ones or the subscriptions. Do you still need 4 TV subscriptions? Do you need that gym membership?

Year 6: Supercharging Your Investments

In year 6, with the same £5000 monthly salary, you decide to get serious about building wealth. You take a hard look at your spending and decide to cut back on things you don’t truly need, redirecting that money into your investments. Let say you shifted £925 from your spending bucket to your investing bucket:

•       Investing: £1925 (38.5%)

•       Spending: £2000 (40%)

By making a conscious decision to reduce your spending, you've nearly doubled your monthly investment contribution. This is how you supercharge your journey to financial freedom.

The Reality Check: Life Happens

Now, I know what you're thinking. This all sounds great in a perfect world, but what about student loans, renovation costs, childcare costs, school tuition fees, and all the other expenses that life throws our way? You're right. This is a simplified example.

But the principle remains the same. By thinking in percentages, you can create a financial plan that works for you, no matter what your circumstances are. You have a more methodical way to move capital around.

• Use this method to build your emergency fund if you don’t have one.

• Use this method to set aside short term savings for a wedding or a house purchase.

The key is to be intentional with your money. Track your spending, identify areas where you can cut back, and make investing a non-negotiable part of your budget.

Your Path to Financial Freedom

Building wealth isn't about getting rich quick. It's about discipline, consistency, and a willingness to live below your means. It's about turning investing into a game, constantly looking for ways to save a little extra here and there. You don’t want to live a life expecting some luck win with the lottery is going to pay for your retirement. This is real life costs of living!

So, I challenge you to take a look at your own finances.

• What percentage of your income are you spending on fixed costs?

• How much are you investing each month?

• Are there areas where you can cut back and redirect that money towards your ‘Sleep- Well Fund’ or your ‘F***-You Money’?

"Do not save what is left after spending, but spend what is left after saving." - Warren Buffet

Your Action Plan

Ready to put this into practice? Here are a few steps you can take today:

• Track your spending: For one month, track every single penny you spend. You can use a notebook, a spreadsheet, or a budgeting app. The goal is to see where your money is actually going.

  • Use my free MFA budget tracker: You can have unlimited inputs and it churns out the percentages for you! No ads, no cookies, no data saved, fully downloadable for your own documentation and completely free! 👇

MFA Budget Tracker

• Calculate your percentages: Once you have a month's worth of data, calculate what percentage of your income you're spending on housing, transportation, and other categories.

• Create your own rule: The 28-15-20 rule is just a starting point recommended by many within the financial industry. Based on your own financial situation and goals, create a percentage-based budget that works for you.

• Automate your savings: Set up automatic transfers from your checking account to your investment account each month, such as my 20% non-negotiable rule. This way, you'll pay yourself first without even thinking about it.

The path to financial freedom starts with a single step. And that step is thinking in percentages.

References

[1] Trading Economics. (2026). United Kingdom Household Saving Ratio. https://tradingeconomics.com/united-kingdom/personal-savings

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