Can I store the Postgres database on a remote drive or NAS box?

Storing the database on a remote drive or on a Network attached Storage (NAS) device is not supported by Taxcalc. The data should be on the same device as the one where the Postgres Service is running. Any other configuration is outside the scope for support by TaxCalc. 

NFS (Network File System) and other remote file systems are not recommended for use by PostgreSQL. They do not have the same file system characteristics as a local file system, and these inconsistencies can cause data reliability or crash recovery problems.

Instead TaxCalc recommends keeping the database local and making your backups to the network drives through the backup utility in Hub > Administration > Database or automating backups through the use of batch files and task scheduler.

If you wish to automate backups, TaxCalc have written an introduction on doing this for the network version of the program. See the Knowledge Base article Automatic backup of TaxCalc on a server for more information.