Error message “No default tax document number found” prompt while trying to save a sales document?
It’s due to you had enabled the “Enable Tax Document Number Management” setting but you didn’t maintain the Tax Document Number Maintenance.
Image below show that you have Enabled Tax Document Number Management in Tools > Options > Goods and Service Tax.
1. If you don’t need this feature to be enabled, you can disable it from Tools > Options > Goods and Service Tax. (just uncheck the checkbox)
2. If you are using this feature, go to GST > Tax Document Number Maintenance; maintain a new Tax Document Number.
Note: This feature is used in other countries where the government controls the tax document numbers.