Can we place restrictions on the vouchers?

There are some restrictions on vouchers but these are set by the supermarkets themselves. Full details can be found in the below table.

If you wish to impose further restrictions we advise that the best way to achieve this is to write on to the unique message that goes with each voucher link that the vouchers are to be spent on grocery items only. 

Whilst this is not technologically true, it's a prominent message and the dominant, centre-of-screen piece of content that each recipient will see.  As it's the intended purpose of the buyer, it will be interpreted by most as being part of the spending rules of the voucher.

Brand What can't they be spent on?
Aldi Aldi or third party gift cards
Lottery tickets, scratch cards or related material
Alcohol
Asda Third party concessions
Gift cards
Tobacco
Stamps
Petrol
Lottery tickets
Iceland N/A
M&S N/A
McColls Exclusions:
Branded gift cards
PayPoint and PayZone products and services including bill payments and E top-ups
Mobile top-ups
Oyster
Postage stamps
Lottery tickets and games including scratch cards
Cigarettes, tobacco and e-cigarettes
HND accounts
Morrisons Gift cards
Lottery tickets
Sainsbury's An up to date list is available here. It includes:

Branded Gift Cards
All lottery related products
PayPoint products and services
Stage 1 Infant Formula milk
Tobacco and related products
Postage stamps
All in store concessions
Petrol and Diesel
Mobile phone top ups
Online delivery charges
Travel Money
Tesco Gift Cards
Waitrose Tobacco and tobacco products
Postage stamps
Scratch cards
Lottery tickets
Infant milk formula 0-6 months
Prescription products
Mobile top up
Gift cards
Pay cards
Car park charges