Partial 1031 exchange question regarding "taxable boot"

[Sarah Minor]

I have a question regarding timing.  Here is the scenario.  If I sell my investment property for 1.3 and the strike value is 1.1 for replacement property, there will be a 200k taxable boot.  My question is this.....when does one actually receive the boot money minus the taxes owed for cap gain?  Does it get paid at the closing of my relinquished property or at the closing of the replacement property?  I hope that makes sense.  Thanks for any information regarding this situation.