Tax planning/advisory services engagement letter

When a taxpayer requests tax planning/advisory services do you have a stand-alone engagement letter for that service or do you include it in the tax return engagement letter?

We do separate engagement letters if it is a significant amount of time expected to be spent.

My personal tax engagement letter includes a paragraph that specifies the type of tax planning is covered by the engagement, and that if additional work is to be done that it will be a separate engagement.

Tight engagement letters are a good defense in case anything ever goes to court (though in +40 in practice between my father and I, we’ve only ever had one thing go to court or be claimed on insurance).