If you are filing your VAT return by post or your VAT return is being posted online outside of Tally you still need to let Tally know that you have filed it to ensure your records are correct.
To file your VAT return in Tally but not online you follow the same process as if you were filing online. If you have the HMRC online filing feature enabled within your account then you need to ensure that you disable this before you submit the return within Tally. You can do this by going to Settings>VAT Settings, and bottom of this screen you need to untick the Enable Online Filing option.
Then go to Reports > General Reports > VAT management & Reports. Fill out the report dates and check the number. You then need to click Submit to HMRC. This will not send it to HMRC however it does tell Tally you have submitted it yourself.