Once Proposals are sent to clients they transition to a Pending status.
To transition a Pending status Proposal to closed, you must first open the Proposal on web.
Click the More menu in the top right:
Click Mark as Lost/Void:
Add text to the Note section and confirm by clicking Mark as Lost
If you need to void a proposal with a payment attached, you must refund the payment first. To refund, login to your Payabli dashboard, and find the needed transaction. There are three dots to the right of the transaction, click these to find the refund button. If you aren't seeing the refund option on a brand new transaction, you'll have to wait 24-hours for that payment to settle.
Once the transaction has been refunded and removed from the proposal, you'll be able to void.