Free Tool · No Signup

T-Bill Calculator Kenya

See your real net earnings on Kenyan Treasury bills after withholding tax and bank custody fees. Compare 91, 182, and 364 day options at the same capital. All in Kenyan Shillings.

Your T-bill

Adjust any field to see how it changes your net earnings.

KSh
Amount you receive at maturity. Minimum KSh 100,000, in multiples of KSh 50,000.
Shorter tenor means faster access to your capital. Longer tenor usually pays more.
% per year
Pull the latest from CBK. Recent range: 91-day 7-9%, 182-day 8-9%, 364-day 8-10%.
%
Standard rate is 15%. Confirm current KRA rules. Set to 0% only if you qualify for exemption.
% p.a.
Typical range 0.10-0.50% per year. Set to 0% if you invest directly via DhowCSD.
KSh
Flat fee some banks charge per purchase. Often 0 via DhowCSD.
Your Results

What you actually keep

Net interest you keep
KSh 0
After tax and all fees
Effective net annual yield
0.00%
Gross yield: 0.00%
You pay today
KSh 0
Discount of KSh 0
Tax & fees deducted
KSh 0
WHT, custody, and transaction

Where every shilling goes

Your gross interest, less what gets taken before it reaches your account.

Net interest (yours)
Withholding tax
Bank custody fee
Transaction fee

91 vs 182 vs 364 day, side by side

Same capital, same tax and fee assumptions, three different tenors. The yields below default to recent CBK auction levels. Adjust each if you have more recent data.

Calculating...

Your full breakdown

Line item Amount Notes
Ready to track your portfolio?

The full Excel template

Log every T-bill, watch your net interest add up across the year.

This calculator is great for single scenarios. But when you actually start buying T-bills, you need a place to record each one. The full Karatasi T-Bill Tracker is a complete Excel workbook for managing a real portfolio across the year.

  • 20-row purchase register with auto-calculated maturity dates, prices and net interest
  • Plan vs actual dashboard that updates as you log each buy
  • Side-by-side comparison of 91, 182, 364 day tenors at any capital
  • Goals page with built-in feasibility check
  • Educational tabs on the discount mechanism, withholding tax, and DhowCSD vs bank routes
View the template →

Excel workbook · 7 sheets · One-time purchase

Preview of the Karatasi T-Bill Tracker Excel template showing inputs and net earnings breakdown.

The two things this calculator does that others don't

Most T-bill calculators show you the headline yield and stop there. That's the gross figure. It's what the auction quotes, but it isn't what lands in your account.

Two things get deducted before you see a shilling. The first is withholding tax, usually 15% on the interest. The second is bank custody fees, which most commercial banks charge for holding government securities on your behalf. Both are taken automatically, but if you're not paying attention, you may not notice how much they cost.

The real cost of bank custody

A KSh 500,000 T-bill at 7.8% with 0.25% custody fee and 15% WHT. Going via your bank vs directly through DhowCSD:

Net (via bank)
KSh 7,953
Net (via DhowCSD)
KSh 8,265
Difference
KSh 312

Custody fees are usually quoted annually but charged proportionally to the tenor. On a 91 day T-bill, the 0.25% annual fee works out to roughly 0.06% of face value. Small per investment, but it adds up.

91 vs 182 vs 364 day, what actually matters

All three tenors are sold weekly (the 364 day is monthly). They have the same minimum, the same minimum increment, the same tax treatment. The differences are yield and liquidity.

How to use this calculator

T-bills vs the alternatives in Kenya

Once you have the net yield from this calculator, here's roughly how it stacks up against other Kenyan saving options.

Common questions

How do Kenyan Treasury Bills work?

T-bills are short term government IOUs sold at a discount. You buy them for less than the face value, and the government pays you back the full face value at maturity. The difference is your interest. They come in 91, 182, and 364 day tenors. Minimum investment is KSh 100,000, in multiples of KSh 50,000 thereafter.

What is withholding tax on T-bills in Kenya?

Standard withholding tax on T-bill interest is 15%, deducted automatically by the Central Bank of Kenya or your bank. Always confirm the current rate with KRA, as tax rules can change. The calculator defaults to 15% but lets you adjust it for any exemptions that may apply.

What bank custody fees should I expect?

Most commercial banks charge an annual custody fee of 0.10% to 0.50% of face value for holding government securities on your behalf, prorated for the tenor. Some banks also charge a flat transaction fee per purchase. Investing directly through DhowCSD (CBK's mobile platform) avoids bank custody fees entirely.

Which T-bill tenor is best?

It depends on your goals. The 91 day tenor gives the fastest access to your capital but the lowest yield. The 364 day tenor locks in today's rate for a full year, usually at a higher rate. The 182 day sits in the middle. If you expect rates to fall, longer is better. If you expect rates to rise, shorter is better. A ladder of staggered T-bills smooths out reinvestment risk.

How does the discount mechanism work?

Unlike bonds, T-bills do not pay periodic coupons. For a 91 day T-bill at 7.8 percent yield, you pay roughly KSh 98,055 today for a KSh 100,000 face value. After 91 days, the government pays you the full KSh 100,000. Your KSh 1,945 gross interest is the difference. Withholding tax and any custody fees are deducted from that interest.

How do I actually buy a T-bill in Kenya?

Two main routes. The cheapest is DhowCSD, the CBK's mobile and web platform. Open a CDS account directly (free, takes 1-3 days), then bid on auctions yourself. No bank custody fees. The other route is through a commercial bank or investment bank that runs a CDS account on your behalf. They charge custody fees but handle the paperwork. Both let you place non-competitive bids, which guarantee allocation at the auction's average rate, and which are recommended for retail investors.

Is this calculator accurate?

It uses the standard 365-day year convention applied by CBK to calculate discount, purchase price, and effective yield. Withholding tax and custody fees apply exactly as you enter them. Real auction outcomes can vary slightly depending on settlement timing, secondary market trades, and any bank-specific fees not captured in our two fields. Treat it as an informed estimate, not a guarantee.