Nice! tests/balance/pretty.test could be a good place. hledger/doc/balance.m4.md is the place to document the new flag. This will be great for bs/is/cf as well, rendered by Hledger/Cli/BalanceView.hs I think.

I notice the top and left lines are double and the bottom line is single. Would it be better to flip these, so the double line emphasises the grand total ?

Alright, tests & docs added and I also added support for this option in BalanceView.

I notice the top and left lines are double and the bottom line is single. Would it be better to flip these, so the double line emphasises the grand total ?

I don’t think so. The bottom line separates the totals from the individual values while the top line separates titles from the individual values. IMHO totals and individual values are more closely related (e.g. they are both numbers) than the titles and the values.

In accounting reports I think it's traditional to use a thick/double line below columns of numbers, highlighting the grand totals. What do others think ?

(NB this visual difference in line weights is more or less visible depending on the font, for anyone wondering..)

Thanks!