Is it possible to make corrections to estimates and invoices once they have been generated? Or does one need to delete the old document and create a new one from scratch? On a similar note, is it possible to re-render an estimate or invoice using a different template?

I've got the same problem and found no out-of-the box solution. So here is a workaround: I make a backup before generating an invoice and roll back if my invoice is not so proper. It's not elegant but better than nothing. I think to alter an invoice or an estimet is a would be nice feature. Greetings Matjazsch

Sending a revised estimate
An estimate is an approximate calculation of your project cost and time requirements. The Estimate tab shows the slips you have created to guess the time and cost of a project; these slips correspond to single line items on an estimate.

Unlike an invoice, Billings stores the estimate slips in the Estimate tab even after you have sent an estimate. If you want to send a revised estimate, simply alter the slips and send the estimate again.

To send a revised estimate:
1. Select a client.
2. Select a project for the client.
3. Click the Estimate tab.
4. Open the affected estimate slips by double-clicking them. Make the necessary changes and click OK.
5. Choose Slips > Send Estimate.
6. Enter the appropriate information. Click Create.
Billings sends the estimate according to the delivery option you have specified.

Billings stores a link to the sent estimate in the Links tab of the project window.

To correct an invoice, you actually must delete the first invoice. The reason that slips disappear "into" an invoice when you send it is to prevent double-billing etc. This essentially ensures good accounting practices.

Anyhow, it's quite easy to "correct." Basically what you do is delete the invoice first. Billings will prompt you to make sure you want to delete the invoice. Then, it will ask you if you want to make the slips active again. That means that the slips will be put back on the Working Slips tab, where you can edit them and send the invoice again.

The process is slightly counterintuitive, and we will work on a solution, but in the meantime this is how you can get your slips back to correct an invoice.

- this will help - works fine .
This was a verry serious issue for me - I tought about not to buy "Billings" if there is no solution - but now consider it bought Tank you Adam