Basic Information

Why am I getting gap limit fillup TX?

These transactions occurs when you have consecutive 20 unpaid orders. To prevent your HD wallet from not discovering your future payments, blockonomics will do a small TX to the 20th address to keep things going. For more technical details, it is recommended to read this article  

Why are the charges so high?

Please note that these are not any extra charges from Blockonomics. The charge reflects the amount of transaction fee needed to confirm the TX on the bitcoin network. In period of high congestion, these fee will become high and during low activity, they will decrease. You can use this utility to view the current state of the bitcoin network.

How can I avoid these charges?

Electrum has a configuration to increase the gap limit setting (the process is shown below). It is also worth investigating any display issues on your website that may be causing so many unpaid orders. 

Using Electrum to increase Gap Limit

Advisory Note

 It is recommend to do this if and only if you are facing large amount of charges. Be advised that changing gap limit is a risky procedure with the following risks:

  • Other HD wallets like trezor, ledger, don't support this setting. So if you recover your electrum seed into another wallet, you may find some funds as missing
  • You have to remember/store the gap limit setting along with the wallet seed words to successfully recover wallet from seed words
  • Higher gap limit leads to low performance of wallet (like slower startup time).


  1. Switch to electrum wallet to receive your merchant payments. If you are already using electrum, you can goto Step 2
    i. Download Electrum wallet and get its XPUB (extended public key)
    ii. Copy your existing HTTP Callback URL from Merchants and keep it safely
    iii. Delete your existing wallet xpub from Address Watcher and add the electrum XPUB
    iv. Goto Merchants > Settings and Paste back the HTTP Callback URL you copied earlier and Save Changes

  2. Set Gap Limit in Electrum Console. Use the following command to set the gap limit (You can use any number between 20-200):


    Using electrum console to set Gap Limit
  3. Restart electrum and verify that gap limit has been set properly. If you type following in the console it should print the expected gap limit setting:

  4. Set same Gap Limit in Blockonomics for your XPUB using  this utility

 Setting Gap Limit in Blockonomics