“My partner wants me to change an old file note now that there’s a complaint.”

You've already answered the hardest part: you don't want to do this, and you're right. Don't amend the note.

A file note has value because it was made at the time. Changing one after a dispute has arisen, so that it records advice you don't recall giving, creates a false record. If the file is produced, that record could mislead the person or body assessing the complaint. The professional risk sits with whoever made the change, and on these facts that would be you.

Say no to the task, not to the person. You don't need to accuse your partner of anything. Frame it around protecting the firm: "I'm not comfortable changing the original note now that there's a complaint. If it's ever examined, an amended note will do us more harm than the original. If you recall giving that warning, the safer course is a separate note, dated today, setting out what you remember and when." A dated supplementary note is legitimate. It is also transparent about when it was written, which is the point.

Put it in writing afterwards. A short email confirming the conversation is enough: you discussed the file note, the original stands, and any recollection will go in a separate dated note. That isn't hostile. It gives both of you a clean record.

Know where to go if it escalates. If you're pressed again, or you find the note has been changed by someone else, call your law society's ethics line. Those calls are confidential, and the ethics staff field this kind of question regularly.

Keep perspective on the relationship. A partner who asks this under pressure and then accepts a clear no is still the person you've respected. One who keeps pushing has told you something important. In either case, your name is on that note. Your reputation will outlast this job.

If you need advice about your own professional obligations, contact your law society's ethics service or speak to a qualified practitioner.