Publisher Rogers Weed said Microsoft is postponing the shift mainly because "we're not ready with a billing solution that we think is satisfactory for our customers."
Billing issues are dogging Microsoft's attempts to turn its Web media and services business into a revenue and profit generator. Last month, Microsoft said it was fixing a Microsoft Network billing backlog.
"We do remain committed to a business model involving subscriptions," Mr. Weed told Advertising Age on Oct. 17. "We don't think Slate can be self-sustaining just on advertising revenues. That's why we're announcing a fairly specific delay rather than something more general."
Curiously, Slate Editor Michael Kinsley just three days earlier, on Oct. 15, promoted Slate's pending move to a subscription service in a talk at the Magazine Publishers of America's American Magazine Conference in Bermuda. Whether Slate will be successful in charging users remains to be seen, Mr. Kinsley explained, but "somebody is going to figure this out and I think we have a good chance."
Slate has been free on the Web since it launched in June. Microsoft last week announced Slate also would be included in the $19.95-a-month flat-rate service it starts in November for MSN.
Mr. Weed said Microsoft is "very upbeat about going to paid subscriptions."
"Overall we feel like the magazine is in great shape at this point," Mr. Weed said. "Our first challenge was to introduce it to the Internet and establish it within the overall political, policy and cultural dialogue of the country. We think we're making good strides in that area."