Fixed term bonds generally have a minimum opening amount – and most will also have a maximum opening amount too.
Some fixed rate bond accounts can be opened with as little as £1, but typical minimum deposits start at about £500. Maximum deposits can go in to the millions, but only the first £85,000 will be protected by the FSCS (where applicable). You may find the most competitive rates require a larger deposit – although, this isn’t always the case.
Once you’ve made your initial deposit you can’t usually add to it.