The landlord gas cert, drafted before you've packed the analyser.
CP12s are the bit nobody pays you for. You do the checks, then sit in the van filling boxes — copying the same landlord details for the fifth time this week — and you still have to remember the reminder next year.
Dictate the readings on the way back to the van. Hint fills the Gas Safe CP12 to current spec, carries the landlord and appliance details over from last year, books the 11-month reminder and chases the customer's signature so the cert files itself.
Free to start. Open it and have a go — pay only when it's pulling its weight.