How to return variance value from a column using a unique ID, using the last row entry.

[katresolver]

I have an employee payroll spreadsheet and I need a formula to show any difference between monthly net pay.

There is a unique ID for each employee in column A and the net pay amount is in column Q. I want the variance to be shown in column W.

E.g. Employee 19 had net pay of £1000 paid in August, this is shown in cell Q728, in July they were paid £1050, this is shown in cell Q678. In cell W728 I want it to say -£50.00.

I want to be able to track these difference each month. If in June they were paid £2000 cell W678 it should show a value of -£950.00. It needs to the vertical column for the last value. The date is in column C.

[PaulM100]

I'm not sure about your data layout, but here is a formula that will show you the variance between current date and data for last month:
=IFERROR(Q1-LOOKUP(2,1/(A:A=A1)/(C:C=DATE(YEAR(C1),MONTH(C1)-1,DAY(C1))),(Q:Q)),"")