I don't think it is straight-forward, a the tax year starts on 5th April,
which could be any day of the week, whereas WEEKNUM functions are based upon
a week starting on a particular day.

If the week number is solely based upon the start date, then use

=INT((target_date-tax_year_start_date)/7)+1

--

HTH

Bob Phillips

(replace xxxx in the email address with gmail if mailing direct)

"Trevor Aiston" wrote in message
...
Is there a switch I can use with weeknum function that will calculate week
numbers based on UK tax year rather than calender year?

TIA

Trevor