Worksheet calculations very slow...how to improve and/or make efficient

Hi All,

I've been working on a little project regarding Tax payments etc.

It consists of 3 worksheets, which are fundamentally:
1) putting the values in,
2) a VAT / Tax calculator and,
3) a year on year summary sheet.

I am happy with the way the projects inputs values etc but if I include the summary sheet, the dreaded " calculating 2 processors" warning rears its ugly head and the time taken to do anything is a lot lot longer.

If I remove the year on year summary, then everything works OK, and so could someone please have a look at this and see where I can make improvements / use alternative methods to get the same results.

I attach the file in two forms....one with no summary and one with.

Hope you can help as this project is very very close to finishing!!

Regards,

Skyping