I put this here mostly because I forget how to do it and have to make multiple starts to get it right.

I have a wrapper.txt file that consists purely of settings and including my files for my globals (accounts, commodities, automated transactions, and tags so that the --pedantic passes), my transactions, and my balance-assertions.

--pedantic
include globals.txt
include opening_balances.txt
include transactions.txt
include balance_assertions.txt

$ CUR=
$ PREV=$(($CUR - 1))
$ ledger -f wrapper.txt print \
>  -b ${PREV}
>  -e ${CUR} > ${PREV}.txt

$ ledger -f wrapper.txt equity \
>  -e ${CUR} \
>  -l "commodity == 'USD'" \
>  ^Equity: ^Assets: ^Liabilities \
>  | sed '$s/\>  .*//' \
>  > temp_equity.txt

$ ledger -f wrapper.txt print \
>  -b ${CUR} > temp_transactions.txt

$ mv temp_equity.txt opening_balances.txt
$ mv temp_transactions.txt transactions.txt

Note: I keep my ledger files in git so I have a fair bit of freedom to experiment. If I mess things up beyond repair, I can always git reset --hard to revert to the most recent snapshot. I recommend you make a backup as well.

To make this easier, I start by setting a few variables for the current year and the previous year. This allows me to update one variable then copy/paste the rest of the instructions to close the books in subsequent years.

The first print step pulls all transactions beginning (-b) after the previous year and ending (-e) before the current year into ${PREV}.txt as an archive.

Next, I create a temporary file containing the Opening Balances for the period ending (-e) before the current year using the equity command. In my case, I also want to limit my commodities (-l "commodity == 'USD'") to "USD" only because I don't want to carry forward my gallons-of-gasoline and the like. Similarly, I only want Equity, Assets, and Liabilities because I've found that including Income & Expenses gives me some unexpected results at times. I also use sed to make the final "Equity:Opening Balances" transaction an auto-balancing transaction.

Finally, I need to filter out all those archived transactions so I use print to select only the transactions beginning (-b) on ${CUR} into a second temporary file.

At this point, we can move the temp_equity.txt back atop the original opening_balances.txt and move the temp_transactions.txt back atop the original transactions.txt file.

With all that, I usually run a ledger bal to verify that everything balances as I expect. If so, I add the ${PREV}.txtwrapper.txt and updated transactions.txt files, commit them, and push them out to my other hosts.