I have sent a small parcel outside UK but I forgot to put stamps on, what will happen?

If you fail to put stamps on letters or small parcels the parcel will be held at their local sorting office and the receiver will get a postcard asking them to pay the cost by either fixing stamps to the postcard and returning it, the minimum is around £1.20 for a letter so a parcel is going to be a lot more, or taking the card with ID to the sorting office and paying there, you can't pay the postman anymore its all done via the sorting office, if they don't pay you will get it back but it will be held at the sorting office for a few weeks.

If it had your return handle on it, it would in many situations come again to you for inadequate postage. yet once you had no return handle, the positioned up workplace will grant it postage by way of addressee and that guy or woman can verify to the two pay the postage, or no longer settle for the letter. If the addressee won't settle on your letter and there is not any return handle, it is going to the ineffective letter workplace, who probable shreds it after a whilst

I would be very interested to learn how you managed to send a parcel without stamps, as you can't just pop a parcel in the post box. It has to be weighed and verified first.

noticed you said overseas I think it'll just be returned to you but can take a few weeks.

It won't be delivered and probably won't come back. For international parcels they don't go anywhere unless you have taken the parcel to the Post Office, had it weighed, got the correct stamps on it and a customs declaration. As you haven't done that it is likely to be impounded.

depends how far the parcel gets until someone notices theres no stamps. Most likely it will get delivered to the return address. (but it could be delayed)