You will need to use the TSImport module for that and design a template to match up your CSV file fields to Timeslips fields.  I've done many of them if you need some help, but it would be a billable event for me.

The Generate Bills report has an option to print envelopes after printing the bills.

But if you want to print them later, I would try the Envelopes report, filtered by Client Last Bill Date.

Nancy Duhon, Esq.
Duhon Technology Solutions, LLC
Master Certified Consultant for Sage Timeslips
Providing individual Consultations and Third Party Remote Desktop Support - including older/unsupported versions.
404-325-9779
[email protected]

Thank you so much, I have used TS Import before but it was many moons ago.