The XNPV and XIRR functions return the NPV and IRR for cash flows that are not necessarily periodic, they are written as equals XNPV, open bracket, and then it asks for three things for the rates, values, and dates. The rate is the discount rate you want to apply to the cash flows. The values are the future cash flows, and the dates are the dates which the future cash flows will occur on. They are those non periodic dates.

XIRR is written similarly as equals XIRR, open brackets, and then it asks us for three things, values, dates, and then guess. Values and dates are the same as for XNPV, i.e. the value of the cash flows and the date that they occur on the XIRR can sometimes return multiple results. And because of this, there's this optional guess If you have an idea of what your IRR might be, for instance, there may be a positive IRR and A negative IRR from our calculations, then you can put your positive guess into the formula and then Excel can focus on that guess, and it will ignore the negative options.

The regular NPV and regular IRR functions have trouble taking non periodic cash flows into account, but XNPV and XIRR solve this.

An example is where future cash flows may be periodic. Well, that's great. We don't need XIRR or XNPV yet, but the initial cash flow, IE, the investment cash flow, that may be on a random date in the middle of a year. A real life scenario for this is where we're acquiring a company and that acquisition dates can happen on any day in the year, but the returns we earn from that investment in the future, IE, the cash flows earned by the company thereafter. They're often at year end, so those return cash flows, they're periodic, but our investments dates was not periodic.