Staff entertaining - annual events exempt £150/head

Employers are able to exempt annual staff events based on the cost per head being below £150 (EIM21690). Is the cost per head based on the number of staff physically present or the number of staff originally booked for? For example, if an event is pre-booked for 50 staff at a cost of £7,000 - this would result in the cost per head of £140 (and therefore total cost is exempt). However, if only 45 staff actually attend, the cost per head increases to £156 (and therefore above the exemption threshold). There is no entitlement to get a refund for those who didn't attend so the full cost remains payable. In this example, should you use 45 or 50 to work out the cost per head?

Hi paul307130,
Please see:
EIM21691 - Particular benefits: annual parties and other social functions: examples
Which shows that it is calculated on employees "attending" which would mean it would be those who actually attend.
Thank you. 

If the invoice states 50 places and is non-refundable for last minute no-shows then the total remains divided by 50 (one would assume!). Ultimately, do you actually make a log of who does and doesn't attend after the event?

Hi ElectricianInOxfordshire,
Potentially, HMRC could request evidence to show the numbers attending and how you came to it being not taxable.
Thank you.