Tesco coupon policy, do they accept vouchers for things you haven't bought?

A question about : Tesco coupon policy, do they accept vouchers for things you haven't bought?

I did do a search for this but the threads I found were from 2006 so I wasn't sure
Okay so last time I was in tesco and had a few vouchers, the woman scanned them all (including a couple for things I hadnt bought) and it came off the total of my shopping
But this was a self service checkout and she didn't know what I had bought
Do they actually officially accept vouchers if you havent bought all of the items?
I have quite a few vouchers from writing to companies and want to go and spend them tomorrow, I will be buying at least one thing from each brand that I have a coupon for but that leaves a fair bit of leftover money on the coupons which will come off my total shopping bill
Is that technically allowed?
It's just that I don't want to finish scanning loads of shopping only to be refused!

Thanks for reading and I hope that all made sense!

Best answers:

• No, Tesco only accept vouchers for items you purchased.
  You used to be able to use any coupons with your shopping but they changed it a few years ago.
• And it's strict too, I had a voucher for 1/2 price bin liners but on 25's only. I had the 30's (not noticing the difference on the shelf) and the SA rejected it so I put them back.