Hello! I sent payment but left default transaction fee and my payment hasn't been processed yet (its well over month now). I use Bitcoin Core 2 version v0.15.1 (64-bit). For some reason its impossible to increase the transaction fee. I don't know what to do now ;/ will the transaction be canceled over time and my btc returned? Can I cancel it somehow? Thank you!
You can remove this transaction (and all other unconfirmed transactions) from your wallet. Let me quote myself to safe typing:
You can manually remove the transactions from Bitcoin Core:
-Exit Bitcoin Core
-Backup your wallet.dat, even though you should have a backup already, make another backup
-Start Bitcoin Core from a command prompt with options -zapwallettxes -rescan (if you're using a pruned wallet, you can't use this)
Depending on your hardware, it will take a few hours to rescan. After this, your transactions should be gone, but Bitcoin Core might pick them up from mempool again. In that case just wait for it to drop again.
Full description of the commands:
-zapwallettxes=<mode>
Delete all wallet transactions and only recover those parts of the
blockchain through -rescan on startup (1 = keep tx meta data e.g.
account owner and payment request information, 2 = drop tx meta
data)
-rescan
Rescan the block chain for missing wallet transactions on startup
