In the 1980s when I was a programmer and consultant at Hoskyns in London I was invariably the last to fill in my weekly timesheet. I hated timesheets. They were an unreasonable intrusion. How I spent my time, I felt, was no one’s business but my own, as long as I was doing a good job.

Now, thirty years later, I’m the designer of a timesheet system and I go around the world telling everyone how important timesheets are. Who would have thought it?

So many of our youthful enthusiasms and prejudices seem unreasonable as we age. Platform heels, cheese-cloth shirts, transcendental meditation, Chianti flasks with candles, the music of John Cage, Tony Blair, all seem inexplicable enthusiasms now. How odd It seems that I thought it was no business of my employer to know how I spent my working time.

But getting consultants to fill in their timesheets is just the first battle of many if you’re managing a professional services firm. Getting your consultants to tell the truth is the second and larger battle. These are some of the voiced and unvoiced reasons why consultants don’t record time accurately:

• ‘I always put eight hours. It’s the easiest thing to do.’
• ‘I didn’t feel I could charge the client. I don’t think the work I did was really worth what he’d have to pay.’
• ‘I don’t want my boss to see that it took me so long.”
• ‘I never charge more than a whole day, even if I work extra hours.’
• ‘It’s a fixed price project and there aren’t any hours left.’
• ‘I don’t like to charge for time I spend on research. The client expects me to know what I’m talking about.
• ‘It was only a few minutes work. Not worth recording, surely.’
• ‘It’s an internal project. No one minds how many hours I record against it.’
• ‘I made a little mistake on the project. It really didn’t take me long to put it right.’
• ‘I wanted to make it really perfect, so I spent some of my own time on it.’
• ‘I know we need more work of this kind, and we won’t get it if we’re completely honest about how long it takes.’
• ‘I won’t get my bonus if I don’t hit 35 chargeable hours a week.’
• ‘This client doesn’t care how much we charge. The other one does. So I put all my time on the first one.’
• ‘The work was useful for two of my clients, so why not record it twice. We can charge them both.’
• ‘I can’t record time correctly because the law doesn’t allow me to work overtime.’

You can penalise staff who don’t submit their timesheets by reducing their bonuses or applying some other harsh measure. Making sure they tell the truth is a matter of explanation and encouragement.

But without knowing how long tasks take you’ll never know if you are charging too much or too little for the work you do, and you’ll never know if you’re staff are working too hard or just idling their time away.

So, try to convince your staff that timesheets must be done on time and must be truthful. And if there’s a young man in platform heels and a cheese-cloth shirt listening to some weird modern music, and scowling, tell him to grow up!