In a statement, Immigration NZ said it had dealt with Ms Lawson as if she had been excluded so it could get the visa application done quickly, but had not waited for corroboration from authorities.
"In assessing Ms Lawson's visa application we were aware of issues reported in the media about her inability to travel to the United States. In order to process her visa in a timely manner we erred on the side of caution and decided to process her visa as a special direction. This was in case it transpired that she was excluded from travel to the US.
"We have now had an opportunity to review the information supplied as part of her work visa application and we have determined that she is not currently excluded from travel to the United States. As a result Ms Lawson will not need a special direction for future travel to New Zealand unless her circumstances change."
Ms Lawson will visit next month to do more advertising work for Whittaker's chocolates.
A spokesman denied it was an embarrassing mistake for the department, saying it had needed to process the application swiftly so had not waited for the corroboration of her exclusion.
"We've now got some corroboration and it doesn't seem 100 per cent confirmed that she had been excluded from the US."
In a statement last weekend, Immigration NZ said they had needed to invoke discretion in order to issue Ms Lawson with a visa because "Ms Lawson has been excluded from another country, namely the United States" so was ineligible for a visa under normal circumstances.
Under New Zealand law, people who have been denied entry to another country or New Zealand in the past are ineligible for a visa but there is discretion for officials or ministers to override that using a "special direction."
Reports at the time said that although she was denied entry on that trip, she had been advised to apply for a visa at a US Embassy.
"Obviously all the media reports initially in the UK were that she was excluded from travel. When we are assessing applications a lot of open source material like media reports are taken into account but you obviously have to corroborate things as well to check it is correct.
"Not everything comes through straight away. That's why we erred on the side of caution thinking there are all these reports saying she's been excluded so a special direction is the best thing to do in terms of making sure the visa is processed as quickly as possible."
He said it happened in other cases as well because the speed the visa was needed.
