Calculating Quarterly Dates In a Query

[whisp0214]

I need to create a Payment Due date based off of a shipment date by quarter. Simply put, all Shipment dates between 1/1 and 3/31 need to calculate as 4/15. Dates between 4/1 and 6/30 need to be 7/15, 7/1 through 9/30 need to be 10/15 and 10/1 - 12/31 need to be 1/15. I have tried the Dateadd function with limited results. I can lock in the day so it is always 15, but i can not figure out how to get the months correct. Any suggestions?

[ArviLaanemets]

On fly:

=DateSerial(Year(YourDate),INT((MONTH(YourDate)-1)/3)*3+4,15)