One supplier said he is now considering employing a debt collection agency to get payment for the thousands of pounds he is owed by the conservation charity, claiming he has been waiting months for the money owed.
The NTS has cited problems with their new computer systems for the delays. However, firms waiting to be paid said the trust had also blamed computer glitches last year when problems arose.
One supplier, who does not want to be named, said: “We’re chasing money at the moment. It’s a high four-figure sum. We’re only one of very many suppliers in the same position.
“It’s slightly unbelievable that the trust is behaving like this. They assured us last year that all their IT problems had been fixed.
“It’s not that they don’t have the money. Visitor attractions like Glenfinnan, Glencoe and Culloden are raking in enormous takings.
“My underlying worry is that something’s wrong. We will keep chasing for the money, we need to claw that money back from them.”
Another supplier, who also wanted to remain anonymous, said good will towards the charity among suppliers was drying up.
“I’ve been waiting months for my money and getting nowhere when I email or phone,” the supplier said. “I can only deliver within a certain radius, so they are a great market for me. But at the same time, they sell our goods at greatly marked-up prices in their shops and we don’t see the benefit of it, which is galling right now.”
Last September the trust was forced to temporarily suspend its members’ subscription direct debit payments during its IT system upgrade after a small number of members had the wrong amount being deducted or being actioned on the wrong day.
In November, a number of membership direct debits were taken from bank accounts two days early. The trust said this was due to “human error” and not the new IT system.
Simon Skinner, chief executive of the trust, which has about 365,000 members, said: “In stages over the past year, the trust has been introducing new IT systems designed to modernise its financial and customer services processes.
“As with every major project of this type, there have been teething problems.
“Unfortunately these problems have taken longer to resolve than anticipated due to a proprietary software bug. We have been working with the software provider to fix this issue and it is now resolved.
“In the interim, we attempted to notify all suppliers of the issues. We also offered assurances that we had manual systems in place to ensure that they continued to receive payments, but there were inevitable delays, in part due to ensuring the validity of invoices. We are now working hard to ensure all monies outstanding are paid as soon as possible.”
Mr Skinner added: “The trust is in good financial health, continues to be a going concern and is committed to making all outstanding payments quickly.
“Should any supplier be experiencing serious difficulty due to the delays, we urge them to contact us as soon as possible. We regret any upset or concern caused.”