Next Payment Date

Question

I am wondering how to calculate the next payment date a client has. We know when their payment date starts, what the frequency of their payments is, and of course today's date. However, I cannot seem to figure out how to calculate when their next payment is when we know what their frequency of payment and payment start date is.

For example. If they started paying on 1 Jan 2019, and they pay weekly, I want the output (knowing today is 15 Jan 2019), to be 22 Jan 2019.

The formula I currently have is:

=IF(L4="Weekly",M4+7, if(L4="Bi-Weekly", M4+14, If(L4="Monthly", EDATE(M4,1), if(L4="Semi-Monthly", "Manual", "Error"))))

L4 being the frequency based upon a drop-down list, and M4 is the start date.

However, it of course only returns the payment date immediately following the start date.

Any help would be greatly appreciated!

spreadsheet here

Answer 1

=IF(L9="Weekly", (IF(WEEKNUM(M9) = WEEKNUM(TODAY()), M9+7,
                  IF(M9+7 * (WEEKNUM(TODAY())-1) = TODAY(), M9+7 * (WEEKNUM(TODAY()+1)),
                  IF(M9+7 * (WEEKNUM(TODAY())-1) < TODAY(), TODAY()+6-WEEKDAY(M9),
                  IF(M9> TODAY(), M9+7, M9+7 * (WEEKNUM(TODAY())-1)))))), 
 IF(L9="Bi-Weekly", M9+14,
 IF(L9="Monthly", EDATE(M9,1),
 IF(L9="Semi-Monthly", "Manual", "Error"))))

Answer 2

I was able to solve my entire solution with:

=IF(L4="Weekly", if(today()<M4, M4+7, (M4+(roundup(((today()-M4)/7))*7))), 
 IF(L4="Bi-Weekly", if(today()<M4, M4+14, (M4+(roundup(((today()-M4)/14))*14))),
 IF(L4="Monthly",if(day(today())>day(M4), DATE(year(today()), month(today())+1, day(M4)), DATE(year(today()), month(today()), day(M4)))    
,IF(L4="Semi-Monthly", "Manual", "="))))

Based on the answer of "Mark My Answer".