The conversation nobody wants.
WHEN IT IS NECESSARY
Your costs rose You underpriced at the start Exchange rate movement affected your upstream costs The service you provide has expanded
HOW TO DO IT
Give notice. Sixty days is reasonable.
Explain briefly and without apology. "Costs have risen and prices will increase from X to Y from the first of next month."
Do not over-explain. A paragraph of justification invites negotiation.
WHAT TO EXPECT
Most clients accept it. Some will ask. A few may leave.
Losing a small proportion of clients to a price increase is usually still net positive.
EXISTING VERSUS NEW CLIENTS
You can raise prices for new clients first and grandfather existing ones for a period.
That is gentler and it means your revenue only improves gradually.
WHAT TO AVOID
Raising prices without notice Raising them repeatedly in a short period Apologising so much that it invites a discount request
THE BETTER APPROACH
Price correctly at the start. Increases are difficult and price reductions are impossible to reverse.