Bitcoin sent, recipient claiming not received I sent bitcoins to the address I was given (double checked). The recipient is claiming they did not receive it. I sent them a different payment yesterday at 8:30p and they didn't get it until 4:00am so could there be a lag also with this payment? Or are they lying? Please see below for btc address. I sent it this morning at 8:30am.

1LGSCBLrrX8pBehwRxUvZU29UAmVAX6jjZ.
The address received 0.07014343 BTC in 3d727e3f4565e011c0348f813c2d5480210b6bae2003a0f7abaa949d1a7c599a. These coins have already been spent, so at the very least the recipient's wallet provider is aware of the transaction. Depending on the type of wallet, the recipient's account may not have been credited due to internal system issues.

Alternatively, the recipient has received the funds and is trying to scam you for an additional payment.

In either case, your initial transaction is successful, and the recipient needs to work with their wallet provider. You should not send them any more funds.



Checking if a transaction is complete

Due to the attention this question is receiving, I'll go through some of the best practices when checking the finality/completion/status of a transaction.

For a Bitcoin transaction to be complete and irreversible, it must be mined into a block. 

To check if a transaction has been mined, you can check a block explorer. Block explorers are websites that read information from the blockchain and make it accessible to people who are not running their own node. Some commonly used explorers for Bitcoin are blockchain.com, blockchair.com, blockstream.info, and btc.com (no affiliation to any of these).

When you look up the transaction, such as with the link above, you're presented either with a page detailing the transaction, or some form of a not found error.

If a transaction is not found, it has almost certainly not been mined - in this case, you should aim to rebroadcast the transaction instead of sending a new one. It is possible that the transaction has actually been broadcast and just not picked up by the explorer yet, so sending a second one may result in a double payment.

If a transaction is found, it may be listed as unconfirmed. In this case, just wait until it is confirmed. If a transaction is already confirmed, you should see some indication of the block it was mined into (either in the form of a block number, or a block hash starting with a bunch of 0s). If a transaction is confirmed, then it is complete and irreversible.

The recipient says they didn't receive the coins

There are a handful of scenarios in which the recipient may not see the coins even after the transaction is complete:


The recipient's wallet is out of sync/not updating correctly - this is a more common scenario when using exchange or other hosted wallets, or using a regular wallet with a spotty or weak internet connection. In this case, the recipient must check with their wallet provider to locate and credit the coins. 
The address is incorrect - Either you made an error while copying the address, or the recipient provided an incorrect address. In this case, you should work with the recipient to figure out who needs to absorb the loss as the coins are most likely irrecoverable.
The recipient is attempting to scam you - once a transaction is complete, only the recipient can access, locate, or otherwise try to work with the coins. If they insist they haven't received them, it is not due to an issue on your side, and you may be getting scammed.


Things to note


Do not use an explorer recommended to you by the recipient - it is trivial to build an explorer that hides certain transactions and makes you believe they are not complete when they are. Always use multiple third party explorers if you must. Ideally, you should run your own instance of Bitcoin Core with -txindex enabled and check the transaction yourself, but that is not feasible for many users on short notice.
If you really do need to resend the coins, first make a transaction to your own wallet that sends the entire balance to yourself and wait for that to confirm. This prevents you from accidentally paying twice if the initial transaction was simply not broadcast properly. 
Be patient - transactions with low fees can take a couple of days to confirm during high network activity periods - if you see an unconfirmed transaction, just wait.