All transactions that take place over the Bitcoin network require a miner fee to be attached in order to incentivize the network to process the transaction. Since the network can only process a limited number of transactions per second, transactions with a higher miner fee are prioritized over those with a lower miner fee.
The Bitcoin network congestion can vary and can increase the time it takes for a transaction to be confirmed. This can cause wait times of hours or even days for transactions with an insufficient miner fee attached. To avoid this, ShapeShift charges a flat miner fee for every Bitcoin transaction we facilitate regardless of the size of the transaction. This miner fee ensures that our users are able to receive their funds as quickly as possible without experiencing delays due to network congestion. However, we do keep an eye on the best miner fee and update the fee to reflect the network conditions. You can see all our current fees here.
This can disproportionately impact smaller value transactions. For example, if you attempt to deposit BTC to ShapeShift for an exchange but the timer has expired and the funds are returned to you, the miner fee will be deducted from your refund. Likewise, if you are expecting an output from ShapeShift of BTC after a successful exchange, you will also receive the deposit less the miner fee.