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Before you interpret a result
Base results are gross: they exclude taxes, fees and inflation. Add costs as cash flows when evaluating an investment. NPV depends on the discount rate; an IRR alone does not describe risk or guarantee a future return.
Example rates are educational, not current quotes. Official rates are identified with their source and date on CETES auctions.
Conventions and sources
We start with a 360-day basis: the commercial year is a convention for turning actual days into a fraction of a year. For example, 28 days is expressed as 28/360, not 28/365. This does not change the calendar or assume every month has 30 days. CETES price = face value / (1 + simple annual yield × actual days / 360). Dated cash flows let you choose actual days/360 or actual days/365 (the XIRR convention). IRR is effective: even on a 360-day basis, compounding means it can differ from the simple CETES auction yield. NPV includes the initial cash flow at t=0. Periodic IRR and effective annual IRR are shown separately; nonconventional cash flows can have multiple solutions.
Banxico: technical description of CETES · CFA Institute: bond duration and price sensitivity · Discounted cash flows, NPV and IRR