The Bank estimates that 20%-24% of notes in circulation are used or held for day-to- day transactions. In 2018 it estimated that up to a further 5%, or between £1 billion and £3.5 billion, was held by UK households as savings. This leaves about £50 billion worth of issued bank notes whose whereabouts or use is unknown. These notes may be being used overseas for transactions or savings, or held in the UK as unreported household savings or for use in the shadow economy. The Bank does not have enough data even to make broad estimates of how much should be apportioned to each category.44 Stocks of notes