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The short answer
At an assumed 12% a year on a 365-day basis, ₦500,000 for 90 days earns ₦14,794.52 gross. After 10% withholding tax (₦1,479.45) you receive ₦13,315.07, so ₦513,315.07 in total. A 90-day deposit earns roughly a quarter of the annual rate, not the full rate.
Ninety days is one of the most popular fixed deposit tenors in Nigeria because it keeps money out of reach long enough to earn a better rate than a savings account, without tying it up for a year. The most common mistake is reading the quoted annual rate as what you will earn in three months. This example shows the actual sum.
The example set-up
All numbers here are an example. The rate is an assumption for illustration; your bank will quote its own.
- Principal
- ₦500,000
- Tenor
- 90 days
- Assumed rate
- 12% a year (example only)
- Day count
- Actual days ÷ 365
- Interest
- Paid at maturity
- Withholding tax
- 10% of interest
The calculation
- Gross interest = ₦500,000 × 0.12 × 90 ÷ 365 = ₦14,794.52.
- Withholding tax = 10% × ₦14,794.52 = ₦1,479.45.
- Net interest = ₦14,794.52 − ₦1,479.45 = ₦13,315.07.
- Paid back at maturity = ₦513,315.07.
Notice the scale: a 12% annual rate produces about 2.96% gross over 90 days (90 ÷ 365 of a year), and about 2.66% after tax. That is the figure to weigh against what you could do with the money in the meantime.
Why the day count matters more on short tenors
Banks express rates per year, but they divide by either 365 or 360 when they work out the interest for a part-year. Standard Chartered Nigeria's fixed deposit page, for instance, states a 365-day basis for naira and GBP and a 360-day basis for other currencies. On the same example:
| Basis | Gross interest | WHT 10% | Net interest |
|---|---|---|---|
| Actual/365 | ₦14,794.52 | ₦1,479.45 | ₦13,315.07 |
| Actual/360 | ₦15,000.00 | ₦1,500.00 | ₦13,500.00 |
The gap is ₦184.93 net on ₦500,000. Small, but when you compare offers from two banks quoting the same rate, the basis decides which pays more. Our guide to how fixed deposit interest is calculated goes further.
About the tax
BusinessDay reported in February 2026 that banks were applying the statutory 10% withholding tax to interest, starting with January 2026 statements, and that for individuals it is final tax. You will usually see the gross interest and the tax as separate lines on your advice or statement. This is information, not tax advice; see withholding tax on interest.
Count the days to your maturity date
"90 days" means 90 calendar days, not three calendar months. A deposit booked on 2 November 2026 matures 90 days later on 31 January 2027, which is a Sunday. Banks deal with non-working days differently: some pay the next working day, some the previous one, and that can add or remove interest days. Ask your bank, and if you need the cash on a particular date (school fees, rent), book a tenor that matures a few working days earlier.
Rolling it over four times versus one year
If you renew the deposit each time it matures, principal plus net interest, at the same example 12% rate, four 90-day cycles (360 days) take ₦500,000 to about ₦555,425.79. That only holds if the rate stays at 12% each time, which it may not. Rates can rise or fall between cycles; that is the reinvestment risk of short tenors. Our comparison of 30, 90, 180 and 365-day tenors looks at when short terms make sense.
Upfront interest
Some banks offer to pay the interest at the start. Standard Chartered Nigeria's page says upfront interest is paid the day after you apply, and that such deposits cannot be liquidated early or rolled over. Upfront interest gives you cash now, but check the rate: it is often set lower to reflect early payment.
Is 90 days right for this money?
A 90-day deposit suits money you know you will not need for three months but will need soon after: a rent payment due in the spring, a planned purchase, or a business reserve you review each quarter. It suits less well money you might need at short notice, because breaking early usually costs part of the interest, and money you will not touch for a year or more, where a longer tenor may pay a higher rate. If you are unsure, splitting the ₦500,000 into two or three smaller deposits with different maturities keeps some cash coming back sooner; our page on fixed deposit laddering shows how.
Also compare the after-tax figure with simply leaving the money in a savings account. If the savings account pays far less and you are confident about the timing, the fixed deposit wins. If the gap is small, the flexibility of the savings account may be worth more than the extra few thousand naira.
What to check before you book
- The rate in writing and the day-count basis.
- The exact maturity date and what happens if it falls on a weekend or holiday.
- What the bank does at maturity if you give no instruction.
- The penalty for breaking early.
- Any minimum amount for a 90-day placement.
Where Pryme fits
A Fixed Box in the Pryme app lets you lock naira for a term you choose, with the current rate shown before you confirm. Naira deposits are held by Solid Allianze Microfinance Bank, licensed by the CBN and insured by the NDIC up to the applicable limit. See Savings Boxes.
Questions people ask
How much interest will ₦500k earn in 3 months fixed deposit?
At an example 12% a year, about ₦14,794.52 gross over 90 days, or ₦13,315.07 after 10% withholding tax. Use your bank's quoted rate in the same formula: amount × rate × 90 ÷ 365.
Is 90 days the same as 3 months in a fixed deposit?
No. Banks count calendar days. Three calendar months can be 89 to 92 days, so the interest and the maturity date differ slightly.
What happens if my fixed deposit matures on a Sunday?
It depends on the bank's terms. Some pay on the next working day, others on the previous one. Ask before you book if you need the money on a set date.
Can I add money to a 90-day fixed deposit?
Usually not. A fixed deposit is booked for a set amount; extra money is normally placed as a new deposit with its own rate and maturity.
Sources
- Standard Chartered Nigeria: Fixed Deposit Account (undated product page) · accessed Oct 2026
- BusinessDay: Why was withholding tax deducted from savings interest (21 Feb 2026) · accessed Oct 2026
This article is general information, not financial, legal or tax advice. Products described are provided under the terms on this site and are subject to regulation and eligibility.