Table-wise billing
An order builds through a meal rather than arriving at once, so the bill has to stay open, take additions, and close when the table asks. Splitting a bill between guests or merging two tables is an ordinary evening. Keeping the order against the table rather than on a pad is what stops an item being missed off the bill, which in a busy service happens more than owners assume.
GST on food and the right rate
Restaurant GST is not the same as retail GST and the rate depends on the kind of establishment, so it is worth confirming your position with your CA once and then setting it on the items. After that every bill applies it correctly without anyone deciding. The invoice carries your GSTIN and the tax split, which is what a corporate customer claiming the meal will ask for.
What actually sells
A menu carries items that earn and items that only occupy space, and most owners have a sense of which rather than a figure. Sales by item over any period gives you the real ranking, and read against your cost per dish it shows where the margin is. Menus get trimmed on that evidence far more usefully than on instinct.
The number to watch
Day-end cash against the till. A restaurant takes money in cash, UPI and card through a busy service, and a difference of a few hundred rupees a night is a large number over a year. Recording each mode separately and closing the book every night is what turns that from an unexplained leak into something you find the same evening.