I'm going to raise this again as it has been some time since it was last raised, and garnered quite a lot of interest only to be refused.
Customer orders a bike a £500 and a Helmet at £30. Customer then pays £150 deposit against the work order. Customer then says, actually, I'll just take the helmet now. If you then select the helmet to pick up and then go to tender it, the POS then asks for a further random payment, which must be calculated as some percentage of the total deposit, rather than just taking the £30 from the £150 already paid. We have our settings set that we do not require a minimum deposit so there is no reason for an additional payment to be made.
This really feels somewhat amateurish when you find your self asking a customer if they've already collected an item.