adjusted cost base

Think of the way your aunty calculates the real cost of the rice she sells at the market. She does more than remember what she paid the wholesaler. She adds the transport, the bags, the small dash she gave the loader, and only then does she know her true cost, and from that she can tell you her real profit when she sells.

Adjusted Cost Base works the same way, except it is the tax world's version of that careful market arithmetic. It is not simply what you paid for an asset like a house, shares, or land. It is that original price plus other costs tied to buying and improving it, minus anything that reduced its value along the way. This adjusted figure becomes your true starting point when it is time to calculate gain or loss.

Say a Nigerian professional in Lagos buys a plot of land for ₦8,000,000 and later spends ₦1,500,000 on documentation, survey, and fencing. The Adjusted Cost Base is not ₦8,000,000 alone, it becomes ₦9,500,000. If that land is later sold for ₦15,000,000, the real gain used for tax purposes is ₦5,500,000, not ₦7,000,000, and that difference can matter a lot when the tax bill lands.

In the United Kingdom, someone holding shares who pays broker fees when buying and selling will add those costs into the base too, so their Capital Gains Tax is calculated fairly on what they actually gained, not on the raw sale price.

This idea protects you from being taxed on money you never truly pocketed. It rewards the careful record keeper, the person who kept receipts, invoices and proof of every naira or pound spent improving what they own.