The same brief, twice, gives the same file.

A requirement arrives in words and leaves as criteria. Columns are standardised to one definition each, and the original kept beside it. The file ships with its own limitations written down.

Seed insertion

Placing known addresses in the file so you can see for yourself what was sent and when.

Correction

Updating what has changed, wherever a current value can be established.

Change-only refresh

On a repeat build, reporting what actually moved instead of re-delivering the whole file.

If the number you were quoted elsewhere looks too good, send it over.