Double-entry bookkeeping is the reason anyone can trust a set of accounts. The principle is simple: every transaction touches at least two accounts, and the total debits must always equal the total credits.
When you pay UGX 2,000,000 for stock, two things are true at once — your inventory went up by 2,000,000 and your cash went down by 2,000,000. Recording only one half of that tells you nothing useful. Recording both means the books are self-checking: if they do not balance, something is wrong, and you find out immediately rather than at year end.
That self-checking property is what makes a trial balance possible, what makes an audit possible, and what makes a lender willing to look at your numbers. Single-entry cash lists cannot give you a balance sheet, cannot show you what you owe, and cannot be audited.
The practical takeaway for a growing business: the point at which you should move off spreadsheets is not when the spreadsheet gets slow. It is when you need to answer questions a cash list cannot answer — what am I owed, what do I owe, and what is this business actually worth.