# professional.utilisation
The four ratios a professional-services firm (law, accountancy, consulting)
reports for a fee earner, a team or the firm:
- **utilisation**: billable time over available time;
- **billing realisation**: what was billed over the standard value of the time
(the time at standard charge-out rates), so write-downs at billing show up;
- **collection realisation**: what was collected over what was billed, so
write-offs and bad debts show up;
- **overall realisation**: collected over standard value, the product of the two.
All four come back in basis points (10000 = 100%), each rounded half-up to the
nearest basis point from the exact integer ratio, once. None is capped: time
recorded beyond contracted hours gives utilisation over 10000, and billing at
a premium gives realisation over 10000; both are real and worth seeing.
A realisation whose denominator is zero is null rather than 0 or 100%: with no
standard value there is nothing to realise, and reporting 0% would read as a
total write-off. Available time of zero is an error instead, because a fee
earner with no available time has no utilisation to report.
The three amounts must share one currency, and nothing may be negative; credit
notes belong in the billed figure as a reduction, not as a negative period.
How the firm defines "available" (contracted hours less holiday, or a target
of chargeable hours) is the caller's choice; this only divides.