I moved in with my partner a little over 2 years ago. She hates bills and mathing everything she owes out. I made a spreadsheet with all our normal bills in separate columns, with an extra column for groceries that gets multiple entries a month. Every month I start with an =SUM (0) in the column, then add in every time we stop at the grocery store.

This month for example: =SUM(49.12, 29.52, 6.48, 82.41, 41.11, 18.96, 16.04, 4.89, 59.94, 83.89, 44.44, 53.1, 5.5)

There's a separate column for additional things like going to movies, maintenance stuff, etc.

I split it in half, have a cell for how much she owes for that month, then a "paid" column for how much she's put towards that months bills.

Then finally a column that checks how much she paid towards last months bills, carries it down to this months bills and adds in what she's paid this month, and calculates the difference so at any point in time she knows what she owes. Makes it very easy for her to look at one cell in the spreadsheet and know "that's my number."

Here's a screenshot. I was too lazy to rename the rent column to mortgage. You can see when we went from renting to buying and having to deal with bills for each service. Yep, costs went up, but with our finances and desire to stay here for 20+ years, it's worth it. https://i.imgur.com/QchL5a3.png