Prices set at the start of a business tend to be set nervously, and then they stay. Costs rise, the work gets better, the business gets busier, and the figure on the quote is still the one chosen when the main worry was whether anyone would say yes at all. The result is a business working at capacity and wondering why the money does not reflect it.
Delay makes the eventual increase worse. A business that has not moved its prices for four years is not facing a small adjustment; it is facing one large enough that customers notice, which is exactly the conversation being avoided. The same total increase applied gradually would have passed with little comment. Avoiding a series of small awkward moments reliably produces one big one, and postponing it further only raises the figure.
The fear is losing customers, and some will go. What the fear usually misses is which ones. Price rises are felt most sharply by the customers who chose you on price, who are typically the ones who negotiate hardest, pay slowest and take the most time for the least margin. Customers who chose you because the work is good and the job gets done tend to absorb a reasonable increase, because replacing a supplier they trust costs them more than the difference. Losing some of the first group and keeping the second is not a failure of the exercise; it is frequently the point of it.
Delivery matters more than the number. An increase announced with notice, applied from a stated date, and presented as a simple statement rather than an apology is received as ordinary business. Anything that sounds defensive invites negotiation, because it signals the figure is provisional. Existing customers reasonably expect their current jobs to be honoured at the agreed price, and a date far enough ahead to let them plan costs nothing and removes most of the friction.
There is also a quieter route that does not touch the headline rate. Reviewing what has crept into the job unpriced over the years - the extra visit, the small modification, the out-of-hours call - often recovers as much as a percentage increase and is easier to justify, because it is charging for work that is genuinely being done. Whichever route is chosen, the discipline that matters is putting a date in the calendar to review prices annually, so the decision is a routine one rather than a confrontation that has to be worked up to.