Quote from: Meerkovo on May 16, 2013, 02:34 amROFL @HighGirlCmon man, when I have something useful to say I do my best to get it right, why can't some people just stop being lazy and tell me an opinion, oh well not to worry, I will continue to do more research and guess thread can be closed!Cheers anyways guysPrepaid envelopes can be bought with cash in-store from some post offices but not all will stock them. The concern is they are only for first or second class mail within the UK so unsuitable for international deliveries since you can't apply more stamps onto the envelope to top it up as when a serial number is scanned on the envelope, it ignores all other postage marks around it.Packs of C5 sized envelopes you can usually purchase around 100 of them for 95 or around that figure. They come in prepackaged amounts so you can't buy 1 at a time really. As for how they track the individual envelope I don't know, they scan the barcode on the exterior packaging when you pay for them but as far as I know, the barcode on the exterior only indicates the product and price of the item and is the same across all of the other packs.Now, each envelope does have a unique number which is stored by Royal Mail so it may only be used once, but I can't tell you if they know precisely which shop has which envelope or whether they merely package the envelopes into a bundle and sell the bundles off not knowing which envelope numbers are inside. For around 70 you can get 100 of the standard size business mail envelopes with the windows in them, prepaid first class. Again they have individual numbers for prepaid postage but come part and parcel of a sealed bundle.Having said all that however - I have received mail in the past which haven't been franked but look like prepaid envelopes so I may be wrong, but the products I buy certainly contain serial numbers.