How do I write a resignation letter in the UK?

The structure. 'I am writing to formally resign from my position as [title] at [company], effective [last day, calculated from your contractual notice period]. Thank you for the opportunities I have had during my time here. I am committed to a smooth transition and will work with you on handover during my notice period. Yours sincerely, [name].' Three to four sentences total.

What NOT to put in the letter. Reasons for leaving (these belong in the conversation with your manager, not on file). Complaints (will be used against you in references). Specific information about your new role (no need to disclose). Emotional language (the letter is a legal record, not therapy).

Timing. Have the resignation conversation with your manager FIRST, then send the letter the same day or next morning. The letter following the conversation reads as professional process; the letter arriving without warning reads as confrontation.

Email vs printed. Email is now standard at most UK employers. Print and sign if your contract specifically requires (some senior contracts do). For senior roles, consider both: a brief email to your manager + HR, and a signed printed copy at the same time.

After you send. Don't disclose your new employer until your current company asks. UK employers are entitled to know the dates and that you're going to a new role; they're not entitled to know which company unless you specifically agreed to disclose in your contract. Some senior roles have non-compete clauses that change this.