How to use "We require to know" or " We need to know" in an official correspondence?

How to use "We require to know" or " We need to know" in an official correspondence? How it is used when correspondence being done a. Within the organization and b. Outside the organization.

From Fowler's Modern English Usage, Second Edition:

The construction with a to-infinitive, as in

I require to know your names,

is not idiomatic in BrE, but is known in other varieties of English.

I'd say that the passives 'You are (not) required to ...', 'Are we required to ...' etc are totally idiomatic, if rather formal.

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'We need to know ...' is totally grammatical, but lacking previous context is abrupt.

'As new regulations mean that we have to update our records, we need to know ...'.

'To help us expedite your order, we need to know ...'.