Which formula to use to compare 2 spreadsheets that have 6 columns?

How about using a Helper Column + Concatenation

Instead of comparing each column individually, combine all six columns into one string per row and then compare those strings. This drastically reduces the complexity.

Step 1: Create a Helper Column in Both Sheets

In SheetA, insert a new column (say, column G) and use this formula in G2:

=A2 & "|" & B2 & "|" & C2 & "|" & D2 & "|" & E2 & "|" & F2

Do the same in SheetB, also in column G.

The | symbol is just a separator to avoid accidental matches (e.g., "Bank1Code2" vs. "Bank1|Code2").

Step 2: Use COUNTIF to Compare

In SheetA, next to your helper column (say, column H), use:

=IF(COUNTIF(SheetB!G:G, G2) > 0, "Match", "Missing")

This checks whether the combined row from SheetA exists in SheetB.