"mmm1106" wrote in
message ...

can anyone tell me why this formula works
=IF(AND(G7<(TODAY()-15),I7=TRUE),"OK","contract required")

but this one doesn't

=IF(AND(G7<(TODAY()-15),I7=yes),"OK","contract required")

it's driving me mad...

Because unless you have defined yes as a name, Excel doesn't recognise it.
If you want to look for yes as a text string, you need to put it in double
quotes, just as you've done with the strings "OK" and "contract required".
By contrast, TRUE is a logical value which Excel recognises.
--
David Biddulph