Big Technologies tumbled 26% as it warned revenues from a prisoner tagging contact with a major customer in Colombia are coming to an end.
Costs are also rising to fund an expansion into the US, the statement said, with margins to be affected until sales pick up to reflect the investment.
That news overshadowed a trading update stating that revenues for the year to end December were £55 million (£50.2m) and underlying profits (adjusted Ebitda) £35m (£30.5m).
Sales this year (2024) are expected to drop to around the level of 2022 (£50m) but this will depend on how the situation in Colombia unfolds, it added.
A return to growth is expected in 2025, the statement concluded.
Shares fell 31p to 95p.