In converting an Annuity to a Cashflow, I believe the initial payment is being handled incorrectly.
Here is code that demonstrates that:
(* Annuity with an initial payment and then 5 payments *)
(* Present value *)
TimeValue[Annuity[{pmt, {init}}, 5], 0, 0]
(* init+5 pmt *)
(* value before the first period *)
TimeValue[Annuity[{pmt, {init}}, 0], 0, 0]
(* init *)
(* value after the first period *)
TimeValue[Annuity[{pmt, {init}}, 1], 0, 1]
(* init+pmt *)
(* convert the annuity to a cashflow *)
cf = Cashflow[Annuity[{pmt, {init}}, 5]]
(* Cashflow[{{1,init+pmt},{2,pmt},{3,pmt},{4,pmt},{5,pmt}}] *)
(* We have lost the fact that the initial payment was made first *)
When I went to post this on Mathematica StackExchange I found an earlier post from 6 years ago. If I am correct about this being a bug, it would result in a wrong result.
Why hasn’t this been fixed?