Most people know roughly what they earn and roughly what they spend, and are surprised when the two do not match. A small set of Excel sheets turns the guessing into numbers you can act on, and makes tax time much easier. You do not need special software or accounting skills. You need four sheets and twenty minutes a month.

Sheet 1: Income and expenses

The foundation is a log of every shilling that comes in and goes out, with a date, a category and an amount. Start with the simple income and expense log, which keeps a running total and shows your income, expenses and net result. Record entries weekly. Use categories you will actually remember, such as rent, food, transport, school fees, airtime and savings, and use the same names every time so the totals add up.

Sheet 2: A monthly budget

A budget is a plan for the month ahead. Take your take-home pay and assign it to categories before the month starts. Our guide to how to budget on a Kenyan salary after deductions shows a sensible split, and the monthly income and expense planner gives you a ready layout. If you are not sure of your take-home pay, use the net to gross salary calculator or the PAYE calculator.

Sheet 3: Savings goals

Give each goal its own line: an emergency fund, school fees, a deposit for land, a holiday. Record what you save each month and how much is left to reach the target. The savings and sinking fund tracker does this, and shows the progress of each goal. Pay yourself first by moving money to savings on payday, not at month end.

Sheet 4: A tax file

Keep one sheet for tax: your income by source, the tax already deducted and the reliefs you claim. The individual tax return workpaper lists sources of income, allowable deductions and tax paid, and totals them for your return. Add the figures from your P9, rent records and any business income. The tax reliefs calculator shows how insurance, pension and other reliefs reduce your tax.

A twenty-minute monthly routine

  1. Download your bank and M-Pesa statements for the month.
  2. Add any entries you missed to the income and expense log.
  3. Compare actual spending with the budget and note where you went over.
  4. Move your savings and update the goal sheet.
  5. File the payslip and any receipts that support reliefs.

The routine is boring, which is why it works. Do it on the same day each month.

Keep your documents with your sheets

Spreadsheets are only as good as the evidence behind them. File payslips, statements and receipts in a folder named for the year, as described in how to organise your tax documents through the year. The receipts and invoices filing index records where each document is kept, which saves time when you need one.

After three months, you will see patterns. Which categories grow every month? Where does the money go in December? Are you saving as much as you planned? Use the answers to adjust the budget. People who track their spending often find the extra money they were looking for without earning a shilling more.

Protect the files

Your finances are private. Protect the workbook with a password, store copies in two places and avoid emailing them. Save a new copy each month with the date in the name, so you can go back if you make a mistake. If you share finances with a partner, agree who updates which sheet.

When to move to something bigger

An Excel system is enough for most households and small side incomes. If you run a business as well, move the business records into a proper cashbook and keep them separate from the household sheets; see separating business and personal money. Start simple, keep it up, and refine it as your needs grow.

Common mistakes to avoid

Three habits spoil most personal spreadsheets. The first is trying to track everything in too much detail, which makes the routine so long that you stop. The second is mixing business and household entries in one list. The third is never reviewing the results. Keep categories few, keep business separate and spend five minutes each month asking what the numbers say and what you will change next month.