Unpaid rents and council tax bills are the bane of many councils. But raising council tax isn't the only way to solve the problem. We know; we've been working with Hammersmith & Fulham LBC, one of only four London authorities not to raise their council tax this year. Together, we've found a way to build stronger relationships with residents and bring in more money – and it all starts with writing better letters.

Last Christmas, for example, Hammersmith & Fulham collected an extra £20,000 in one month by simplifying a rent arrears letter. But the even bigger difference came from the residents who couldn't pay right away. After writing the letter in a more personal tone, calls from people wanting to talk about their situation or arrange repayment plans went up by 16% – saving the council even more money in costly collection processes.

So what makes a letter ‘better'? It's about getting the balance of efficiency and empathy right. Here are three things to think about in order to make your communications more effective:

Replacing the stick with the carrot works wonders. It's easy to start difficult letters with the negatives – telling people what will happen if they don't pay a bill right away, for example. But we've found that opening with a scolding tone often puts readers in the wrong frame of mind to co-operate. Instead, explain why you're asking them to do something, and offer help to do it, before explaining the consequences if they don't.

Understanding is everything, so cut the legalese. If residents aren't ‘acquitting' themselves as you'd hoped – whether they're playing their music too loud or missing rent payments – resist the temptation to change their behaviour with legalese. It might feel like a good deterrent, but legal-speak is often hard to picture. Would a resident know what ‘recovery action' looks like? Probably not. 

Instead, imagine what you'd say if you were talking to your reader. (Perhaps: ‘If we don't hear from you, we'll have to take you to court') It feels more direct, but also makes you more straightforward. Using language most readers understand breaks a few ‘us' and ‘them' barriers and linguistically puts you on the same side. So readers are more likely to do whatever it is you're asking.

Changing your writing means changing your culture. One thing that's really struck us about our project with Hammersmith & Fulham is the change it has made inside the council. When we started, it was clear that unhelpful templates were holding writers back. As part of the programme, cabinet members and directors gave people licence to change, empowering them to lose the templates if there was a better way to help residents. Officers leapt at the opportunity.

This hasn't just made the writers happier. Residents are more satisfied and the council has more money to spend on services. Everyone wins.

Hannah Moffatt is creative director at language consultancy The Writer.