That big infusion of cash that Congress approved last year to shape up the beleaguered IRS is having an unexpected side benefit.

The funding increase has helped the agency to catch up on processing new and backlogged tax returns. And that, in turn, has allowed federal bean-counters to give policymakers a more precise picture of when the Treasury could run out of money — the so-called X-date — if the government isn’t able to take on more debt.

The nation is stepping uncomfortably close to an unprecedented default that could have catastrophic effects on the global economy because it is bumping up against its legal limit for borrowing. Congress and the White House have been unable to agree on a plan to lift or suspend the borrowing limit