TBILLEQ in Collabora Office: Convert a Bill Discount to an Equivalent Annual Return
Use Collabora TBILLEQ with a bill discount, reproduce the 9.4151% control, and distinguish the equivalent annual return from discount and price-based yield.
Verification status: See the evidence and test scope described in this guide. How formula examples are checked
Quick answer: =TBILLEQ(DATE(1999;3;31);DATE(1999;6;1);9.14%) has documented result approximately 9.4151%. It takes a discount rate as input and returns an equivalent annual bill return.
Syntax and documented date scope
=TBILLEQ(Settlement; Maturity; Discount)
Settlement is the purchase date, Maturity is the expiry date, and Discount is the acquisition discount percentage. All three are required. The vendor’s description says maturity must fall within the same year; the controls here stay inside one calendar year.
The dedicated page does not provide a full numerical maximum-span/error contract. Do not replace its wording with another product’s day-limit rule or infer long-dated behavior from the short example.
Use 9.14% or 0.0914 for the rate. There is no Price argument or optional Basis. A price such as 98.45 entered as Discount would mean an entirely different and inappropriate scale.
Example: reproduce the source’s return
Put =DATE(1999;3;31) in A2, =DATE(1999;6;1) in B2, and 9.14% in C2. Enter =TBILLEQ(A2;B2;C2) in D2.
There are 62 actual days between the dates. The independent short-interval arithmetic consistent with the documented control is:
=365*C2/(360-C2*(B2-A2))
It gives approximately 0.094151493566, or 9.4151493566%, consistent with the source’s rounded 9.4151%. This is independent arithmetic, not a captured native output or a formula contract for every maturity length.
Explain the denominator with a price check
For the same 9.14% discount and 62-day interval, the independent discount-price model is =100*(1-9.14%*62/360), approximately 98.425888889.
The gain relative to that investment price, annualized using 365 days, reconstructs the same equivalent rate: (100−price)/price×365/62. The discount itself is measured on a different base, so it is not surprising that the returned annual rate exceeds 9.14%.
Do not substitute the 98.45 price from the vendor’s separate 9% TBILLPRICE example into this 9.14% calculation without acknowledging that the inputs differ.
Advanced example: compare three rates for a clean interval
Use settlement 2026-01-01, maturity 2026-06-30, and discount 4%. The interval is 180 actual days, and the independent price is 98 per 100 par.
The three independently calculated measures are:
| Measure | Rate |
|---|---|
| Input discount | 4% |
| 360-day simple gain on price 98 | 4.081632653% |
| 365-day equivalent simple return | 4.138321995% |
For the corresponding TBILLEQ call, the independent expected third rate is approximately 4.138321995%. The differences come from price versus par denominators and the annualization basis, not from different underlying cash receipts.
Advanced application: keep the quote and interpretation separate
Build a worksheet with separate columns for settlement, maturity, discount, actual day count, independent price check, and equivalent rate. This makes it possible to audit whether a surprising rate comes from a date, a percentage scale, or a denominator.
DATE constructs unambiguous dates. ROUND can display a rate to the required percentage precision, but keep the original unrounded value for comparisons.
An equivalent simple annual return is not a guarantee that identical short bills can be repeatedly purchased at the same terms. Compounded annual return would require a separate reinvestment model.
Errors and limitations
Check date order, the source’s same-year scope, and Discount entered as a rate. In the independent arithmetic, the denominator 360−Discount×days must stay positive for the ordinary positive-price model used here. A near-zero denominator produces a very large rate and should be investigated rather than hidden by formatting.
The dedicated help does not specify every native error code, long-maturity branch, or invalid-input coercion. The guide deliberately limits its computed expectations to short, same-year controls and does not certify cross-product behavior or actual market outcomes.
Availability and verification
The exact function is documented in Collabora Office 26.04 desktop help, retrieved and reviewed on October 17, 2026. This establishes a documentation scope, not the first release that introduced the function or the last version in which it works; those versions and any retirement date remain unestablished. Collabora Online and mobile support are not inferred from desktop help, nor is behavior in another spreadsheet product.
The examples are documentation-based expectations with independent calculations. They have not been executed in Collabora Office. No application screenshot or native error/coercion certification is implied. Formulas use English function names and semicolon argument separators.
References
- Collabora Office 26.04: TBILLEQ (checked October 17, 2026).
- Editorial testing standards.