A guarantee shows clients and potential clients that you believe in your abilities and the quality of your work. Whether it is a time or a cost pledge make sure
it is something you can honour, because the cost of failure or even perceived failure can be disastrous with unseen knock-on effects, whether in poor reviews or a loudmouthed customer out to get even.
Setting out in writing exactly what is and more crucially, what is not covered, is important. It’s a higher risk but it sends a strong message.