The phrase "at least substantially" is correct and usable in written English.
It can be used to indicate that something is true to a significant degree, but not completely or entirely.
Example: "The project was at least substantially completed by the deadline, even if some minor details were still pending."
Alternatives: "at least significantly" or "at least considerably".
If a state could show that its insurance laws were "at least substantially equivalent" to the new federal standards, the state law would remain in effect, and state officials could enforce the patient protections of state law.
Under the Democrats' bill, states could continue to enforce their own laws if the federal government found that those laws were "at least substantially equivalent to, and as effective as," the new federal standards.
Democrats insist that the state laws must be at least substantially equivalent to the federal standards.
PAGE A25 BUSINESS BANKS SWAY BILLS To Aid Consumers Having won some early skirmishes by teaming with Republican allies, the country's biggest banks may wind up killing -- or at least substantially diluting -- two pro-consumer measures.
Having won some early skirmishes by teaming with Republican allies, the banks now appear to have the upper hand and may wind up killing — or at least substantially diluting — both pro-consumer measures.
Large and small banks and their trade associations in Washington have waged a major lobbying effort to kill the proposal, or at least substantially water it down, so that the new agency would not be able to write new regulations and also enforce them.
Seeing your major competitor disappear, or at least shrink substantially, has to be helpful.
Bankers have waged a multimillion-dollar campaign to kill the agency or at least to substantially weaken the powers the administration would like it to have.
A third of all light trucks and a quarter of cars have at least one substantially underinflated tire, a survey by the National Highway Traffic Safety Administration has found.
To that extent, he appeared to have ended the day no worse off politically, or at least not substantially so, than he began it.
Whereas Catholics were bound to strive to achieve enough good works to please God, the Reformers taught that believers stood before God completely freed of this duty and from the enslaving pride that went with the notion that the believers had achieved or at least had substantially cooperated in their own salvation.
