Write spreadsheet formulas

I need a set of formulas that turns daily sales rows into a clean weekly summary: compute week starting date, sum of sales, number of unique customers, and week-over-week growth. Put week start in column F, sales in G, customers in H, growth in I. Check formula accuracy before I share with the ops manager on Monday.

Before I give these formulas to the finance analyst, make them easy to audit: expose the COUNTUNIQUE and SUMIF logic up top, replace any array formulas with explicit helper columns if it makes the steps clearer, and flag rows where a transaction date is outside the expected range.

I created an array formula to roll daily rows into weeks and the totals don’t match the pivot. Zach in finance will call it out in the review. I’m not sure whether the problem is my DATE boundary logic or an off-by-one in the array. What’s the quickest way to test and correct the formula so my totals align and I can explain the change to Zach?

Every month I re-create the same weekly-summary formulas from scratch because I’m afraid of hidden dependencies and prior mistakes. It costs me hours and makes me late. What habit or small process change will let me reuse correct formulas reliably across reports without reinventing them each cycle?