how long until IRS puts a lien on my home for past due taxes this year?

With that size of a debt, I'd be a bit surprised if you have not already been slapped with a lien by the IRS.

The IRS routinely lifts liens temporarily to allow for sales or refinancing. Any underwriter worth their salt knows how to proceed with that. The IRS does step in and take any cash off of the closing table as part of the agreement to lift the lien to allow the transaction to proceed. Since that's your planned course of action anyway it's nothing to be worried about.

Yes, a lien will cause the refi to fail. If you are making your payments, they probably won't file a lien.

If you owe when you file next year, you will default on the payment plan and all bets are off.

did they agree to that $400 a month? that amount sounds too low for them to accept it,
you can't just set up your own payment plan,,, they WILL put a lien on your home,,, it could take 6 months

Are you running a business and failed to submit income tax withheld from your employees?

You are unlikely to be able to re-finance your mortgage with a 19,000 tax lien. The lender is going to request tax transcripts (IRS Form 4506-T).

until they get paid or arrangements are made to pay it off
and forget the refi you will very likely be denied

Even if you tried before they place the lien we ask for tax returns for the last 2 years. If we see an amount due to the IRS we ask for proof of payment.