The House Account works great for all those regular bills.  With a little thought it can even handle seasonal bills.  With a little fudge-factor, it can handle bills that vary within a range, like cellphone bills.  But what about groceries? And eating out?  And trips to the hardware store?

Enter The Amex Bill.

One account.  Two cards.  One bill.

Bill arrives.   Basics entered:  His Charges.  Her Charges.   Sums up to be the whole bill.

In one column, enter all the charges on his card that are shared expenses.  Groceries.  Eating out together.  Plants  for the garden.  Sum those up as His Shared Expenses.   Divide by a ratio (e.g. 50-50 or the Ratio from The House Account) to get Her Share of His Expenses.   Add Her Share to Her Charges, and subtract Her Share from His Charges.

Do the same for Her Charges.

Each person deposits the amount to cover their new adjusted charges into The House Account, and the bill payer pays The Amex Bill from there.

The Amex Bill.   Good for the marriage.  Good for lots of free flights and rental cars.   Which are also good for the marriage.