I greatly enjoyed this comment and the subthread it inspired.
For the peanut gallery: never give anyone in an extension in writing; your ask should be for immediate performance.
Why? Well, there are a lot of varieties of "performance" which aren't happy outcomes for you. Should you give someone an extension to their deadline and have them perform in a way which is displeasing to you, the default is they do not have a regulatory infraction if you complain [0]. Should someone blow their deadline and then perform and then have you complain to the regulator, they basically always have a regulatory infraction regardless of whether their performance is satisfactory, so their incentive is do whatever possible to prevent the complaint.
[0] Situation dependent, obviously, but lots of regulatory regimes will have an escape hatch like "unless agreed to by the customer" or "unless agreed to by the counterparty in writing."
For the peanut gallery: never give anyone in an extension in writing; your ask should be for immediate performance.
Why? Well, there are a lot of varieties of "performance" which aren't happy outcomes for you. Should you give someone an extension to their deadline and have them perform in a way which is displeasing to you, the default is they do not have a regulatory infraction if you complain [0]. Should someone blow their deadline and then perform and then have you complain to the regulator, they basically always have a regulatory infraction regardless of whether their performance is satisfactory, so their incentive is do whatever possible to prevent the complaint.
[0] Situation dependent, obviously, but lots of regulatory regimes will have an escape hatch like "unless agreed to by the customer" or "unless agreed to by the counterparty in writing."