Stamp duty on a mortgage or debenture instrument.
Stamp duty
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Duty rate
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Total with loan
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The duty on the loan, not the house
When you finance a property with a mortgage, two different documents change hands and each carries its own stamp duty. There is the deed that transfers the property to you, and there is the mortgage or debenture deed that secures the lender's loan against that property. This calculator deals only with the second one. It charges ad valorem duty on the sum the lender is securing, which is the loan amount, at the low rate this tool applies of roughly 0.375 percent.
The word ad valorem simply means the duty scales with value rather than being a fixed fee. Double the loan and you double the duty. The reason the rate is so modest compared with property transfer duty is that a mortgage is security, not a sale. The bank is not buying your house, it is registering a charge it can enforce if you default, so the state taxes the instrument lightly.
A NGN 60 million home loan
Suppose you borrow NGN 60,000,000 to buy a flat. Using the rate this calculator applies, the mortgage deed attracts NGN 225,000 in stamp duty. That figure is the loan multiplied by 0.375 percent, and it is paid once when the security is created and stamped.
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The chart shows the loan amount and the stamp duty side by side, making it easy to see how modest the duty is as a share of the total commitment.
Do not confuse it with the deed of assignment
The commonest and costliest mistake buyers make is to assume the mortgage duty is the only stamp duty on the deal. It is not. The deed of assignment that conveys the property to you attracts its own ad valorem duty, charged at a markedly higher rate of around 1.5 percent of the property value in the model this site uses, and that is often the larger bill by far. On a NGN 70,000,000 purchase funded by a NGN 60,000,000 mortgage, the deed duty can dwarf the mortgage duty. Budget for both lines, plus legal and registration fees, so the closing costs do not surprise you.
Because the rate here is knowledge-based rather than independently certified, treat 0.375 percent as the figure this calculator applies and confirm the current mortgage and debenture rate with the FIRS, reconstituted as the Nigeria Revenue Service under the 2025 reform, before you complete. The mortgage instrument involves a lending company, so it generally sits on the federal side of the stamp-duty divide.
Budget the duty into your closing cash
Timing matters more than people expect. Stamping is one leg of perfecting the security, alongside registering the charge at the land registry and, where the borrower is a company, filing it with the corporate registry. Lenders usually want all three done before they advance the money, because an imperfect mortgage ranks poorly against later creditors. So the NGN 225,000 in the example is not a fee you can defer to tidy up afterwards. It sits in the upfront cash you need at closing, next to the deed duty, the lawyer's bill, and the registry charges. Build the full stack into your deposit planning rather than treating the mortgage duty as an afterthought, because a shortfall here can stall the drawdown on completion day.
Does a debenture work the same way?
Broadly yes. A debenture is a company's charge over its assets to secure borrowing, and it is treated in the same family as a mortgage for stamp duty, charged on the sum secured at the rate this tool applies. So a company raising secured debt can use this calculator the same way a homebuyer would, by entering the principal the debenture secures.
Who pays the mortgage stamp duty?
In practice the borrower bears it, because it is the borrower who needs the security perfected to draw down the loan. Lenders almost always pass the cost through, either as an upfront charge or rolled into the facility's fees. Read the offer letter, since an unperfected mortgage leaves the lender unsecured and they will not release funds until the duty is paid and the charge is registered.