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If you're buying something online or simply paying an individual in Bitcoin, you may be able to copy the information you need to complete the transaction from any type of wallet. However, if you want to pay for goods and services in person, you'll need to have Bitcoin in a wallet you can access on the go, such as a mobile wallet. Many brick-and-mortar merchants use apps, such as BitPay, to process their Bitcoin transactions. To use your mobile wallet, make sure it's compatible with the app the merchant is using. When you download the mobile wallet app, it will tell you which services it is compatible with. The individual or merchant you want to pay will give you the public address for their wallet or account. From your wallet, you'll send your Bitcoin to this address as payment.  Typically, you'll receive an invoice that specifies the amount of Bitcoin you owe the individual or merchant. Because Bitcoin value is volatile, this invoice will only be valid for a brief window of time – maybe 10 or 15 minutes. Many individuals and merchants provide a QR code that you can simply scan with your phone from your mobile wallet app to send your Bitcoin to the right place. Within your wallet app, choose the option to send your Bitcoin to another wallet. Enter the payment information the individual or merchant gave you along with the amount of Bitcoin you want to send them. Then tap or click the button to send the Bitcoin. If you scanned a QR code from within your wallet app, all of this information will be filled in for you. Look over it before you click send to make sure the amount of Bitcoin is correct. Once you submit your payment, the transaction is sent to the blockchain for confirmation. Miners (Bitcoin users with powerful computers) work to confirm the transaction. Typically it takes 10 to 30 minutes to confirm a transactions. Once your transaction is confirmed, it can't be reversed. If you're buying something from a brick-and-mortar merchant, you'll likely get whatever you bought before the transaction is actually confirmed. However, you may be sent another invoice for payment if the transaction isn't confirmed or if it takes several hours to confirm.
Transfer the Bitcoin you want to use to an accessible wallet. Copy or scan the payment information. Send your Bitcoin to the address you copied. Wait for the transaction to be confirmed.